Just installed WordPress 2.3... begrudgingly. I really had no desire to, but since I was already a couple version behind, I thought, what the hell.
WordPress 2.3 really didn't have anything new for me. Sure, it has tagging, but I use (err, used) Ultimate Tag Warrior and loved it.
And WordPress 2.3 likes to break some installs on upgrades. I just edited my contact page and I got an error. The contact form itself works, but editing the page was a pain.