themes (Score 1)

Well, the short answer is that you don't have to run a shitty underlying OS to get a friendly desktop, but both the Qt widget set and KWM (I haven't used any other window managers with KDE) have the advantage of having fully-functional keyboard operational support. By default, you can change applications and focus within applications with just they keyboard. (I've never used GNOME so I can't speak for that)

Also configuration in KDE was made to be GUI-based, rather than the more traditional Xresources config files. (yah, I'm a wuss, we should all configure everything with vi/emacs, right?)

I agree with you that pretty UIs are all well and good, but usability is the bottom line.