WordPress 1.5.1 is out, and given that it included a security fix, it seemed like a good idea to go ahead and upgrade. The upgrade went pretty easily, as near as I can tell. You really can just overwrite the old files, assuming you don’t do like me and drop them into the wrong directory. The only problem I had was with a stats plugin I was using on the admin side and the fact that I really should have deactivated/reactivated the plugins during the process.
And hey, look at that! The subcategories I’ve been too lazy to fix are back. :)