If no bugs are bothering your site then you can just wait for version 3.1. Anyway, here are the bug fixes;
3.0.5.3 - 12/28/10
fixes:
-fixed issue where tooltip was attaching itself to all a hrefs in the admin panels
-fixed colorbox and validation scripts that were not working for some customers
-fixed sidebar blog dates from widget that was pulling todays date instead of the blog date
-fixed required validation for checkboxes and radio buttons.
-fixed featured.php and index.php child theme portability issue
-fixed Enable Blog -> No option.
-fixed the coupons module, multiple bugs were fixed here.
-fixed "relisted ads" to update the listing date to the day it was relisted (shows up as "Just Listed" when relisted)
-fixed broken sidebar tabs when posting a comment
-fixed ad-block class by changing it to post-block to avoid ad blockers from failing to display classipress correctly
-added the registration link back into the login page
-fixed issue where ads only displayed 3 images even when more images were allowed and uploaded
-fixed problem where coupon caused negative ad price to be calculated
-fixed all the bugs associated with the checkboxes and radio buttons on the ad-edit page
-fixed checkboxes and radio buttons so they appear correctly (instead of a drop-down) on the form builder preview page
-fixed positioning issue with form validation error messages on both new ad and edit ad pages
-fixed bug in loop.php where html would show up in ad listings blurb if character count was over 165
-fixed bug where auto-complete search would only work if you were logged in as an admin & "Back Office Access" was not disabled
-fixed upgrade script so it doesn't prompt new installs to upgrade
changes:
-added pagination on the user dashboard page so only 10 ads are listed per page
-added support for custom hierarchical taxonomy permalinks for ad categories (only works in
WP 3.1+)
-added new admin chart dashboard widget showing total sales and new ads over the last 30 days (Small Business Edition or higher)
-added two new advanced settings admin options. turn off wordpress version meta tag & disable admin menu (only works in
WP 3.1+)
-updated appthemes.com urls to include www