You can read about WordPress 2.5.1 and you can download the new version here. WordPress 2.5.1 fixes lots of bugs and Here are some highlights:
- 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 for IE
So to those who have WordPress 2.5, better upgrade soon.