The latest version of WordPress, 2.7, was released earlier this week. The release, code/nick-named "Coltrane", brings several major back-end improvements:
Lorelle lists several reasons to upgrade immediately. Ryan Boren discusses the release, including what features were moved to the 2.8 (or later) blueprint. He also notes that WordPress 2.7 was downloaded 100,000 times in the first 20 hours after release (the counter reads 195,849 downloads at the time of this post), and that some bug fixes are already making it into the planned 2.7.1 release.
I upgraded late last night, and the upgrade went apparently smoothly. As always, let me know if you notice anything amiss. I will be working on some of the new features, such as nested/paged comments, in the near future.