Okay, I think SuSE is about the only distro that defaults to KDE, but Kubuntu certainly seems to be popular.
But I'll add to that, my *limited* experience is that nobody uses Gnome!
I've now installed xfce and lxde on my system, but mostly because I've got fed up with dealing with the fallout of "emerge -u kde" in a kde console window. (The update takes out konsole, which takes out emerge, which leaves me with a mess of an upgrade to sort out!)
I've always been a kde guy, even when nepomuk was enabled by default and had a habit of killing systems... (as somebody pointed out elsewhere, even if it was infuriating, the kde devs did say "we're going to fix it" rather than what I see reported of Gnome guys saying "live with it").