Use empty() for theming, tag consolidation,

empty()
At http://php.net/empty, the comment by 'inerte is my gmail.com username' states that using empty() is about 20% faster than comparison with '' or "" (zero-length strings). Unlike the following comment's suggested !$var, empty() doesn't generate an E_NOTICE. Page.tpl.php uses a variety of syntax:

if ($tabs != ""):
print $tabs
endif;

or

if (count($primary_links)):
print theme('primary_links', $primary_links);
endif;

or

if ($search):

endif;

All three of these usages could be replaced with empty():

if (!empty($tabs)):

if (!empty($primary_links)):

if (!empty($search)):

... and give the same behaviour.

Tag consolidation
To further slim down and speed up the code, instead of the following:
if ($tabs != ""):
print $tabs
endif;
(which causes PHP to process three code blocks), use:

  if (!empty($tabs)):
    print $tabs;
  endif;

or
if (!empty($tabs)) print $tabs
or even
print empty($tabs) ? null : $tabs

This code is easy to read, involves no shortcuts, and will prevent any E_NOTICE errors. This is pretty much the only tweak I can find in Sympal; it's already a wonderfully pared-down theme!