An alternative viewpoint...
I went through this same decision last year after being a PC user since the IBM XT. Because of numerous negative issues with Vista -- and I won't elaborate here in an effort to avoid flame wars -- I went Mac. Yes I had to swallow hard and hold my breath -- for maybe all of three days. Then nirvana. Not only that, I run three Win-only programs in Fusion running XP and it runs faster in a Mac Pro window than it ever did on my Dell Dual Xeon workstation! I can honestly say I feel zero desire to go back to Windows machine --
Best of luck,
Before I spend £1200 on a new Vista 64 bit machine what Macs should I be looking at? Just to compare