I'd like to have the XP mode thing in Professional, but I am cheap, so I stuck with premium.
Really, I think the names are quite ridiculous. What happened to "regular"? Or just "home"? The 'lowest' version is "Premium". Kinda dumb, isn't it? And "Ultimate" sounds a bit over the top. I mean, I would expect something that is "Ultimate" to be the end-all, be-all of operating systems. It could run 1 million applications on a 90 MHz processor AND cook you dinner.