Are you sure? I have 4 gigs in my box and while running the x64 version it uses roughly 27% of that after a clean install. Although there could be a limit to the usage, and adapted to 2 gigs of RAM..
I got my new laptop 2 days ago and installed SP1 last night. I have no previous experiences with Vista, so I can't offer a comparison. I'll let you know how Max and Photoshop fare once I get them installed.
Still don't see any reason to switch to Vista. All it does it eats up a lot of valuable memory no matter how I configure it. Besides, XP pretty much just got mature enough to be usable. I might make the switch in 2-3 years. Or if I need to preview some fancy schmansy DX10 stuff every 30 minutes or so.