Those clever folk at Wordpress say that they're ready to go with version 2.9 release, candidate one.
In a notice, Wordpress said that there's a lot of "fun and geeky" things in version 2.9 to try out.
There's a whole long list of user features, as well as a host of development features and work on themes.
There's also a plugin compatibility feature,
The full list of features is here.