There are a huge amount of small but significant updates in this release. One feature, which Matt talks about in his announcement post, is the addition of a rating system for plugins. Now you can rate how compatible a plugin is with a certain version of WordPress. I think this will prove to be a very useful feature as although there are thousands of great plugins available via their directory, many of them don’t work with the newer versions of WordPress.
Another update I noticed isn’t really significant at all but it jumped out at me. The famous ‘Hello World’ title for the first post has been changed to ‘Welcome’. I must admit a single tear rolled down my cheek when I read that; what were they thinking!!!
For a complete list of changes in 2.9 please view this article. I occasionally download beta versions of WordPress but it’s advisable to wait and download the stable version with live blogs incase there are any bugs. If you do wish to download WP 2.9 RC 1 though you can do so here.
Link : 2.9 Release Candidate 1