Update: WordPress 2.5 has gone final. Great work from the teams at Auttomatic & Happy Cog, along with all of the contributors.
The latest release candidate of WordPress, 2.5 RC2, is out. So far I haven’t noticed any major changes from RC1, just some tweaks based on feedback.
Matt (WordPress co-founder) has put together a quick screen cast as an overview of the major changes compared to earlier 2.x releases. It’s well worth the look
Also, if you are going to upgrade to any release of 2.5, check out the official which plugins work and which don’t list before upgrading. Once you’re in the clear, go install. The admin tool is so much better.