For those of you who are Ubuntuheads and are thinking of upgrading to 12.04, here's my advice - wait.
I'm in the process of upgrading right now, and it's taken the better part of a day so far (with still a couple of hours to go). Everyone and their uncle is hitting that server at the moment.
EDIT: In fact, I'd advise at this moment not to do it - I have a problem or two now that the upgrade has finished - ones I wasn't expecting at all. I'll spend the next couple of hours screaming at the screen and let you know what's happening.
The secret of life is to aim below the head (With thanks to MMM)