A P200 with 128MB RAM and two 1.6GB HDs running WindowMaker was my desktop machine for a couple of years up until Feb 2001 when I gave in and bought a 1.2GHz Athlon. I could afford the upgrade game, but it felt so nice to be able to do almost everything I wanted to do (except games, the main reason for the Athlon) on such a system. And it was quiet (2 fans instead of the 6 in my current machine).
I tried GNOME and KDE every once in a while, but they were either clunky, buggy, or both. When I got the Athlon, I threw RH 7.x with KDE on it for a while. Though it was much snappier, it wasn't as crisp as you'd expect from such hardware. I gave up and putw W2K back on it and haven't been much interested in running Linux on the desktop since. I have been following the projects though. I run Linux in a Virtual PC when the need arises (dev work).
If I ever do go back, it would likely be to WindowMaker and ROX Filer.