Thanks to everyone who tested 2.9.1 Beta 1.? We’re following that up with Release Candidate 1.? RC1 contains a few more fixes, bringing the number of fixed tickets up to 23.? If you are already running Beta 1, visit Tools->Upgrade in your blog’s admin to get RC1.? You can also? download the RC1 package and install manually.? If all goes well, 2.9.1 will be here soon.
Read more: http://wordpress.org/development/2009/12/wordpress-2-9-1-release-candidate-1/