I’m not upgrading yet. Give it a few weeks. I’m sure I’ll run into a few things which don’t quite go according to plan, and it would be handy if someone else hit them first so that I can see the fix on the forums.
Edit: Well, I decided to try it, since the auto-update tool tempted me with the “upgrade” button. But for some reason a 40MB /boot partition isn’t big enough for Feisty… so it won’t let me install!