This module provides filters at the top of the Permissions page for easier management when your site has a large amount of roles and/or permissions. The module was originally created because the excessive amount of checkboxes combined with some jquery activity was causing "Unresponsive Script" js errors on every load and save of the permissions page.
Additionally, the 6.x-1.1 release contains functionality for when the content_permissions module for CCK is enabled. Individual content types will be listed, and when selected will filter the permissions page to only show view and edit permissions for fields contained within the selected content types.
This can also be handy when combined with the Firefox plugin, Checkfox. By combining module and role filtering and then being able to simply highlight the entire page of checkboxes, right click, and then "check" or "uncheck" you can seriously cut down on frustration doing bulk permission changes.
The nice folks over at gotdrupal.com put together a video which demonstrates this module as well as a few other utility modules for managing permissions, you can check it out here: http://gotdrupal.com/videos/manage-drupal-permissions-more-easily
D7 release is now available for testing. I know there was a shift from perms in D6 to permissions in D7 but the humor of having variables like $old_perms has lured me into keeping the term perms throughout the code of this module.
jquerymobile: #1265760: Filter permissions: Cannot see neither filter box nor permissions list