Hey.
I have Vista Premium and love it! The new search looks great, Aero looks pretty (i know that isn't a great reason, but hey I always thought XP looked a little bland..), and the new speech recognition is great. (Try it, takes some getting used to, but I can compose emails wayy faster by dictation with it, plus makes me feel like a starship commander or something).
But yeah, Vista does need a pretty decent machine, 2 GB RAM a must, plus a dual-core processor, as well as a clean drive to install on. I don't mind the UAC too much, it can be useful i suppose to alert me to odd programs trying to do stuff.