I do (via Kubuntu), but sometimes I wish I wouldn't - it has lots of annoying bugs that only appear once in a while (not often enough to invest the time to try to fix them, but often enough to be annoying). The most annoying being that ksmserver-logout-greeter sometimes crashes when trying to shut down. And when I want to shut down my PC, it's usually because I want to do something different right now, so having to spend more time getting my PC to shut down correctly (because otherwise, who knows what might happen) is really annoying. That's why overly enthusiastic phrases like this one about how great KDE is kind of rub me the wrong way...