I keep meaning to learn vim and, in so doing, finally become a [SERIOUS PROFESSIONAL COMPUTER MAN], but KDE, when configured the way I want it, is the perfect development environment for me. I keep coming back to it. I have used every major computer operating system, different flavors of Gnome, XFCE, MacOS, Windows, and Linux under various lightweight window managers. If I need an OS for an older desktop machine, then I generally prefer razor-qt though :)
I've mostly outgrown the whole militant-OS-partisan thing, but I guess I'm kind of passionate about KDE. Passionate enough to write a long-winded thing on the internet, at any rate.
KDE is far from perfect. It's a resource pig until you learn how to use it effectively. But, so is everything else. It does seem like KDE development will chase the latest trends, but I hold out some hope that they might make some concessions for those of us who just want a lightweight system with a few powerful features.