I agree with Wayne and Paul. It's crazy to have more than two OS. Hell, just have one. They should combine Pro and Ultimate and Home and Home Premium.
Anyway, I have used both, and I would definitely go with Pro, because A) Ultimate doesn't give you that much more and Pro is meant for a business environment.
As my IT guy once said and I mean this in a very nice way: "What is it about Home you cannot understand?"
Home is meant for home and Pro/Business (they call it different things in different places). One day it will come back to bite you if you go with Home anything.
If you want the ability to make movies and play games and make DVD movies, then get Home Premium. If you want to work in a business environment, then get Busines/Pro or Ultimate. They also integrate better with fax or scanning although I haven't looked at that yet.
