Actually, I'm going to be upgrading the boards again tomorrow - probably in the morning/afternoon time. I will be upgrading to the beta version of the brand new vBulletin software. I've already installed it to test it out:
http://www.creedfeed.com/vb3/index.php?
This is what the board will be like when I go through with the upgrade. It's basically the same with a bunch of new features added in (or standard, like the Quick Reply).
As far as I know, you will not have to reregister for an account. All posts and users will be moved over to the new board when I run the upgrade. If, by some unlucky chance, the upgrade fails, you may have to register, but that is unlikely.