I have vista and I am not a huge fan of it.. It looks good and has some great features however as an over all I find it very heavy I guess you could call it. My system isn't bad, however on start up and this is with the factory settings and nothing installed, (obviously that's changed a bit) it was using 2gb of memory, which I find somewhat irritating, not to mention there are way to many processes and it freaks me out.
My system is as follows
IntelĀ® core2 Quad CPU Q8200 @ 2.33GHz 2.33 GHz
6.00 GB Ram
And my biggest issue - 64-bit operating system