I recently upgrade a blog of mine from Wordpress 2.2 to Wordpress 2.3.  My wife and I don't post on the blog much (looking for better ideas on how to utilize the site), but it's great to keep around to test the latest and greatest Wordpress has to offer.  In my view, the most important new feature in Wordpress 2.3 is the baseline introduction of tags (also called taxonomy or even categories in other CMS applications).