http://30moons.com/pc_chiapet.php
I have ran win7. Just not for my main pc.
So I take you got a taste of it but never used it enough to be convinced?
I don't notice any ill-effects. I do notice much smoother operation in general, and I have always kept my system in top shape during my xp days (service tweaks, minimal auto-start programs, defrag, etc). Vista/7 always felt smooth enough to take less effort to manage, though some of this is done automatically in the background (defrag, for instance). Dunno, could be partly due to much improved hardware these days, but I am willing to trust it's the superfetch doing its job as it should.
If you ever needed anything so terribly outdated / deserted that it absolutely requires XP, then you always have virtualbox to fall back onto (nlite the xp install for even better experience). I usually keep one around to install **certain unwanted apps that I hate but need** anyway, so it all works out.
Then there is the whole interface thing with the dock-like taskbar and the awesome preview feature. Oh yeah, and 7 does look prettier