I use WinXP, but I’m a pretty big Ubuntu fan as well. My major complaint about Linux over the years has been a feeling that it was just a bunch of egotistic nerds who refused to work together for a common goal - they splintered their efforts to no end. I think MacOSX proved this correct when a funded, managed company could do with Linux (or BSD) what the open source community couldn’t for so many years. Ubuntu (funded by the sellout of Thawte to Verisign) is changing this…
But like nathan, I always go back to windows for “real” work. Call me crazy, but to me, one of the larger gripes about day-to-day linux is that the fonts always look really crappy and their file explorer interfaces always really, really suck. Everything looks really huge and clunky.
Seems like a small thing, but, well, it bugs me.