well if you check out paul thurotts site about vista, its a nice discription.
based on what i know, vista ultimate will basically be like MCE, Home, and Pro combined in the most logical way possible (for example, they won't have the network things from home, but maybe they will have the help menu from home
also, this is still up in the air, but there are some rumors going around that vista ultimate users will have special priveledges... in my mind i see them making almost like a membership, and you need to sign up by being "verified" that you have vista ultimate (kind of like the genuine check). then from there you can do things like get some free downloads other users can't, etc.
but i have heard ultimate is the way to go for gamers... and im just fed up with home, so im getting the ultimate edition (see sig). Its gonna also have something along the lines of TweakUI in there to "boost" performance.
I remember reading this earlier on Paul's site (check google for him) but i think it changed. the vista ult. people will NOT have to "activate" windows... anything above home premium was what i remember...... but again, i think they through that out
So is there a difference between the "Enterprise" and "Ultimate" edition? Not too much... but if you want to have the extra little gizmos and such, go for ultimate.... also it will have much better entertainment than Pro... the MCE entertainment, theoretically.
Paul's site really lures you into it. he goes on saying "blah blah there has never been an operating system release of this magnitude! Blah blah vista......"
Good luck making your choice
(i know mine!!)