There is a mandatory upgrade to WordPress 3.0.2 from all previous versions. This is a maintenance release to fix a moderate security issue which allows a user with an author level access to gain access of the rest of the site. The upgrade is particularly important to blogs with multiple users, and all others.
There should be no valid excuse not to upgrade to version 3.0.2 since WordPress upgrades are easy and painless. All it takes is just one click. I upgraded my blogs just a tad different than most WordPress users. I use Subversion update. I have a script that updates all my blogs all at once. Based on the Subversion upgrade, there are only about a dozen files that have changed.
So, update to WordPress 3.0.2. It should be quick and worth the while.