diff --git a/core/lib/Drupal/Core/Plugin/Mapper/ConfigMapper.php b/core/lib/Drupal/Core/Plugin/Mapper/ConfigMapper.php
index 6c8d0b0..bb9a2ec 100644
--- a/core/lib/Drupal/Core/Plugin/Mapper/ConfigMapper.php
+++ b/core/lib/Drupal/Core/Plugin/Mapper/ConfigMapper.php
@@ -43,7 +43,7 @@ public function getInstance(array $options) {
       $settings['config_id'] = $options['config'];
       return $this->manager->createInstance($plugin_id, $settings);
     }
-    // @todo throw an exception.
+    return FALSE;
   }
 
 }
diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index 5ce5a21..9179332 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -474,10 +474,7 @@ function block_list($region) {
  */
 function block_load($plugin_id, array $conf = array()) {
   $manager = drupal_container()->get('plugin.manager.block');
-  try {
-    $block = $manager->getInstance(array('config' => $plugin_id));
-  }
-  catch (Drupal\Component\Plugin\Exception\PluginException $e) {
+  if (!$block = $manager->getInstance(array('config' => $plugin_id))) {
     $block = $manager->createInstance($plugin_id, $conf);
   }
   return $block;
@@ -546,7 +543,10 @@ function _block_get_renderable_block($element) {
 function block_build($block) {
   // Allow modules to modify the block before it is viewed, via either
   // hook_block_view_alter() or hook_block_view_ID_alter().
-  $id = $block->getPluginID();
+  $config = $block->getConfig();
+  $config_id = explode('.', $config['config_id']);
+  $config_id = array_slice($config_id, 3);
+  $id = implode('_', $config_id);
   $build = $block->build();
   drupal_alter(array('block_view', "block_view_{$id}"), $build, $block);
   return $build;
diff --git a/core/modules/block/lib/Drupal/block/Plugin/system/plugin_ui/BlockPluginUI.php b/core/modules/block/lib/Drupal/block/Plugin/system/plugin_ui/BlockPluginUI.php
index 16358d5..9fc2534 100644
--- a/core/modules/block/lib/Drupal/block/Plugin/system/plugin_ui/BlockPluginUI.php
+++ b/core/modules/block/lib/Drupal/block/Plugin/system/plugin_ui/BlockPluginUI.php
@@ -11,7 +11,9 @@
 use Drupal\Core\Annotation\Translation;
 
 /**
- * @todo.
+ * This plugin provides modifications to the system provided base class. Its
+ * purpose is to provide an overrideable user interface for block selection,
+ * configuration and placement.
  *
  * @Plugin(
  *   id = "block_plugin_ui",
@@ -40,13 +42,15 @@ class BlockPluginUI extends PluginUIBase {
   /**
    * Overrides \Drupal\system\Plugin\PluginUIBase::form().
    */
-  public function form($form, &$form_state, $plugin, $facet) {
-    list($plugin_id, $theme) = explode(':', $plugin);
+  public function form($form, &$form_state) {
+    $args = func_get_args();
+    $facet = isset($args[2]) ? $args[2] : NULL;
+    list($plugin_id, $theme) = explode(':', $this->getPluginId());
     $form['theme'] = array(
       '#type' => 'value',
       '#value' => $theme,
     );
-    return parent::form($form, $form_state, $plugin, $facet);
+    return parent::form($form, $form_state, $facet);
   }
 
   /**
@@ -68,8 +72,8 @@ public function formSubmit($form, &$form_state) {
   /**
    * Overrides \Drupal\system\Plugin\PluginUIBase::access().
    */
-  public function access($plugin_id) {
-    list($plugin, $theme) = explode(':', $plugin_id);
+  public function access() {
+    list($plugin, $theme) = explode(':', $this->getPluginId());
     return _block_themes_access($theme);
   }
 
@@ -83,16 +87,17 @@ public function tableHeader() {
   /**
    * Overrides \Drupal\system\Plugin\PluginUIBase::row().
    */
-  public function row($plugin, $plugin_definition, $plugin_id, $config) {
-    list($plugin, $theme) = explode(':', $plugin);
+  public function row($display_plugin_id, $display_plugin_definition) {
+    $plugin_definition = $this->getDefinition();
+    list($plugin, $theme) = explode(':', $this->getPluginId());
     $row = array();
-    $row[] = $config['subject'];
+    $row[] = $display_plugin_definition['subject'];
     $row[] = array('data' => array(
       '#type' => 'operations',
       '#links' => array(
         'configure' => array(
           'title' => $plugin_definition['link_title'],
-          'href' => $plugin_definition['config_path'] . '/' . $plugin_id . '/' . $theme,
+          'href' => $plugin_definition['config_path'] . '/' . $display_plugin_id . '/' . $theme,
         ),
       ),
     ));
diff --git a/core/modules/system/lib/Drupal/system/Plugin/PluginUIBase.php b/core/modules/system/lib/Drupal/system/Plugin/PluginUIBase.php
index ce84dec..cd9a7bf 100644
--- a/core/modules/system/lib/Drupal/system/Plugin/PluginUIBase.php
+++ b/core/modules/system/lib/Drupal/system/Plugin/PluginUIBase.php
@@ -10,14 +10,17 @@
 use Drupal\Component\Plugin\PluginBase;
 
 /**
- * @todo.
+ * An abstract base class for use in creating sane default user interfaces for
+ * plugins of a particular type.
  */
 abstract class PluginUIBase extends PluginBase implements PluginUIInterface {
 
   /**
-   * @todo.
+   * Implements PluginUIInterface::form().
    */
-  public function form($form, &$form_state, $plugin, $facet) {
+  public function form($form, &$form_state) {
+    $args = func_get_args();
+    $facet = isset($args[2]) ? $args[2] : NULL;
     $plugin_definition = $this->getDefinition();
     $manager = new $plugin_definition['manager']();
     $plugins = $this->excludeDefinitions($manager->getDefinitions());
@@ -36,17 +39,17 @@ public function form($form, &$form_state, $plugin, $facet) {
       '#value' => t('Next'),
     );
     $rows = array();
-    foreach ($plugins as $plugin_id => $config) {
-      if (empty($facet) || $this->facetCompare($facet, $config)) {
-        $row = $this->row($plugin, $plugin_definition, $plugin_id, $config);
+    foreach ($plugins as $plugin_id => $display_plugin_definition) {
+      if (empty($facet) || $this->facetCompare($facet, $display_plugin_definition)) {
+        $row = $this->row($plugin_id, $display_plugin_definition);
         $rows[] = $row;
       }
       foreach ($plugin_definition['facets'] as $key => $title) {
-        $facets[$key][$config[$key]] = $this->facetLink($key, $plugin, $plugin_definition, $plugin_id, $config, $key);
+        $facets[$key][$display_plugin_definition[$key]] = $this->facetLink($key, $plugin_id, $display_plugin_definition);
       }
       $form['right']['all_plugins'] = array(
         '#type' => 'markup',
-        '#markup' => l($plugin_definition['all_plugins'], $this->allPluginsUrl($plugin, $plugin_definition, $plugin_id, $config)),
+        '#markup' => l($plugin_definition['all_plugins'], $this->allPluginsUrl($plugin_id, $display_plugin_definition)),
       );
       foreach ($facets as $group => $values) {
         $form['right'][$group] = array(
@@ -64,65 +67,127 @@ public function form($form, &$form_state, $plugin, $facet) {
   }
 
   /**
-   * @todo.
+   * Implements PluginUIInterface::formValidate().
    */
   public function formValidate($form, &$form_state) {
   }
 
   /**
-   * @todo.
+   * Implements PluginUIInterface::formSumbit().
    */
   public function formSubmit($form, &$form_state) {
   }
 
   /**
-   * @todo.
+   * Allows a given plugin to exclude various defintions form the user
+   * interface via whatever criteria make sense for that plugin.
+   *
+   * @param array $definitions
+   *  The plugin definitions provided by the plugin manager that this user
+   *  interface is exposing.
+   *
+   * @return array
+   *  A modified array of what was passed into the method.
    */
   public function excludeDefinitions($definitions) {
     return $definitions;
   }
 
   /**
-   * @todo.
+   * Generic access check for use with plugins of this type.
+   *
+   * @return bool
    */
-  public function access($plugin_id) {
-    $definition = $this->getDefinition($plugin_id);
-    return call_user_func_array('user_access', $definition['access_arguments']);
+  public function access() {
+    $definition = $this->getDefinition();
+    return call_user_func_array($definition['access_callback'], $definition['access_arguments']);
   }
 
   /**
-   * @todo.
+   * A customized row method for displaying plugins for configuration within
+   * the user interface.
+   *
+   * @param $display_plugin_id
+   *  The id of the specific plugin definition being passed to us.
+   *
+   * @param $display_plugin_definition
+   *  The plugin definition associated with the passed $plugin_id.
+   *
+   * @return array
+   *  An array that represents a table row in the final user interface output.
    */
-  public function row($plugin, $plugin_definition, $plugin_id, $config) {
-    return array($config['title'], l($plugin_definition['link_title'], $plugin_definition['config_path'] . '/' . $plugin_id));
+  public function row($display_plugin_id, $display_plugin_definition) {
+    $plugin_definition = $this->getDefinition();
+    return array($display_plugin_definition['title'], l($plugin_definition['link_title'], $plugin_definition['config_path'] . '/' . $display_plugin_id));
   }
 
   /**
-   * @todo.
+   * Provides individually formatted links for the faceting that happens within
+   * the user interface. Since this is a faceting style procedure, each plugin
+   * may be parsed multiple times in order to extract all facets and their
+   * appropriate labels.
+   *
+   * @param $facet
+   *  A simple string indicating what element of the $display_plugin_definition
+   *  to utilize for faceting.
+   *
+   * @param $display_plugin_id
+   *  The plugin id of the plugin we are currently parsing a facet link from.
+   *
+   * @param $display_plugin_definition
+   *  The plugin definition we are parsing.
+   *
+   * @return array
+   *  Returns a theme_links compatible row array.
    */
-  public function facetLink($facet, $plugin, $plugin_definition, $plugin_id, $config, $key) {
-    return array('title' => $config[$key], 'href' => $plugin_definition['path'] . '/' . $plugin . '/' . $facet . ':' . $config[$key]);
+  public function facetLink($facet, $display_plugin_id, $display_plugin_definition) {
+    $plugin_definition = $this->getDefinition();
+    return array('title' => $display_plugin_definition[$facet], 'href' => $plugin_definition['path'] . '/' . $this->getPluginId() . '/' . $facet . ':' . $display_plugin_definition[$facet]);
   }
 
   /**
-   * @todo.
+   * Provides an "all" style link to reset the facets. the $display_plugin_id
+   * and $display_plugin_definition are provided for convenience.
+   *
+   * @param $display_plugin_id
+   *  The plugin id of the plugin we are currently parsing a facet link from.
+   *
+   * @param $display_plugin_definition
+   *  The plugin definition we are parsing.
+   *
+   * @return string
+   *  returns a simple url string for use within l().
    */
-  public function allPluginsUrl($plugin, $plugin_definition, $plugin_id, $config) {
-    return $plugin_definition['path'] . '/' . $plugin . '/add';
+  public function allPluginsUrl($display_plugin_id, $display_plugin_definition) {
+    $plugin_definition = $this->getDefinition();
+    return $plugin_definition['path'] . '/' . $this->getPluginId() . '/add';
   }
 
   /**
-   * @todo.
+   * Provides a theme_table compatible array of headers.
+   *
+   * @return array
+   *  A theme_table compatible array of headers.
    */
   public function tableHeader() {
     return array(t('Title'), t('Operations'));
   }
 
   /**
-   * @todo.
+   * Compares a given plugin definition with the selected facet to determine if
+   * the plugin should be displayed in the user interface.
+   *
+   * @param $facet
+   *  A colon separated string representing the key/value paring of a selected
+   *  facet.
+   *
+   * @param $display_plugin_definition
+   *  The plugin definition to be compared.
+   *
+   * @return bool
    */
-  public function facetCompare($facet, $config) {
+  public function facetCompare($facet, $display_plugin_definition) {
     list($facet_type, $option) = explode(':', $facet);
-    return $option == $config[$facet_type];
+    return $option == $display_plugin_definition[$facet_type];
   }
 }
diff --git a/core/modules/system/lib/Drupal/system/Plugin/PluginUIInterface.php b/core/modules/system/lib/Drupal/system/Plugin/PluginUIInterface.php
index f90388c..5a557f6 100644
--- a/core/modules/system/lib/Drupal/system/Plugin/PluginUIInterface.php
+++ b/core/modules/system/lib/Drupal/system/Plugin/PluginUIInterface.php
@@ -19,14 +19,29 @@
    *   An associative array containing the structure of the form.
    * @param array $form_state
    *   An associative array containing the current state of the form.
-   * @param string $plugin
-   *   @todo.
-   * @param string|null $facet
-   *   @todo.
    *
    * @return array
    *   Returns the form structure as an array.
    */
-  public function form($form, &$form_state, $plugin, $facet);
+  public function form($form, &$form_state);
 
+  /**
+   * Validates form values from the form() method.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param array $form_state
+   *   An associative array containing the current state of the form.
+   */
+  public function formValidate($form, &$form_state);
+
+  /**
+   * Submits form values from the form() method.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param array $form_state
+   *   An associative array containing the current state of the form.
+   */
+  public function formSubmit($form, &$form_state);
 }
diff --git a/core/modules/system/lib/Drupal/system/Plugin/Type/PluginUIManager.php b/core/modules/system/lib/Drupal/system/Plugin/Type/PluginUIManager.php
index a4f3f8f..abbe63d 100644
--- a/core/modules/system/lib/Drupal/system/Plugin/Type/PluginUIManager.php
+++ b/core/modules/system/lib/Drupal/system/Plugin/Type/PluginUIManager.php
@@ -10,7 +10,9 @@
 use Drupal\Component\Plugin\PluginManagerBase;
 use Drupal\Component\Plugin\Discovery\DerivativeDiscoveryDecorator;
 use Drupal\Core\Plugin\Discovery\AnnotatedClassDiscovery;
-use Drupal\Component\Plugin\Factory\ReflectionFactory;
+use Drupal\Core\Plugin\Discovery\AlterDecorator;
+use Drupal\Core\Plugin\Discovery\CacheDecorator;
+use Drupal\Component\Plugin\Factory\DefaultFactory;
 
 /**
  * Manages discovery and instantiation of Plugin UI plugins.
@@ -21,8 +23,8 @@ class PluginUIManager extends PluginManagerBase {
    * Constructs a \Drupal\system\Plugin\Type\PluginUIManager object.
    */
   public function __construct() {
-    $this->discovery = new DerivativeDiscoveryDecorator(new AnnotatedClassDiscovery('system', 'plugin_ui'));
-    $this->factory = new ReflectionFactory($this);
+    $this->discovery = new CacheDecorator(new AlterDecorator(new DerivativeDiscoveryDecorator(new AnnotatedClassDiscovery('system', 'plugin_ui')), 'plugin_ui'), 'plugin_ui');
+    $this->factory = new DefaultFactory($this);
   }
 
   /**
@@ -33,7 +35,7 @@ public function processDefinition(&$definition, $plugin_id) {
       'default_task' => TRUE,
       'task_title' => t('View'),
       'task_suffix' => 'view',
+      'access_callback' => 'user_access',
     );
   }
-
 }
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 08304f1..2e5e17c 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -1121,7 +1121,7 @@ function system_menu() {
  */
 function system_plugin_ui_form($form, &$form_state, $plugin, $facet = NULL) {
   $plugin_ui = drupal_container()->get('plugin.manager.system.plugin_ui')->createInstance($plugin);
-  $form = $plugin_ui->form($form, $form_state, $plugin, $facet);
+  $form = $plugin_ui->form($form, $form_state, $facet);
   $form['#validate'][] = array($plugin_ui, 'formValidate');
   $form['#submit'][] = array($plugin_ui, 'formSubmit');
   return $form;
@@ -1150,7 +1150,7 @@ function system_plugin_autocomplete($plugin_id, $string = '') {
  */
 function system_plugin_ui_access($plugin, $facet = NULL) {
   $plugin_ui = drupal_container()->get('plugin.manager.system.plugin_ui')->createInstance($plugin);
-  return $plugin_ui->access($plugin, $facet);
+  return $plugin_ui->access($facet);
 }
 
 /**