I too stuck with XP when getting my i7 rig back in spring. In fact, having worked with Vista during my time as a conscript in the army i hated it sufficiently that it was a choice that also determined my RAM size. I stuck with three sticks of 1GB of tripple channel DDR3s, instead of going for something higher because i was sure i wasn't going to install Vista, hence no 64bits and no more than 3.5GB or so.
Maybe we're seeing a repeat of the old progression from win98SE to winME to XP, where winME was the one that didn't do well. Maybe this time it will be XP to Vista to W7, with Vista being the unfortunate stepping stone and we'll have an OS that will work well for the next decade or so in the form of W7.
I'm not going to install them just yet as it's somewhat of a pain to do a full migration. What i want to do is get a second 1.5TB drive first, should be about 100 euros by now, maybe lower, which will allow me to dual boot with XP and W7 without any hassles.