Movable Type 2.6
Movable Type 2.6 has been released and is now running on this site. It has a bunch of fixes and new features. Updating went without a hitch (so far at least) - now I only need to remove the plugins that have been deprecated.
Update: Bugfixes and security patches have been released since I originally wrote this post: 2.61, 2.62, 2.63.