Wordpress today released version 2.5.1 of the the blog software.  This release contains mainly bug fixes and a security update.  From their release notes, version 2.5.1 includes:

Performance improvements for the Dashboard, Write Post, and Edit Comments pages.
Better performance for those who have many categories
Media Uploader fixes
An upgrade to TinyMCE 3.0.7
Widget Administration fixes
Various usability improvements
Layout fixes [...]