I remember that KDE 1 was such a memory hog back in the day. The big improvement in KDE 2 was that it used less memory - but was slow as hell, I went back to KDE 1, then left KDE for good. Of course, "improvements" in GNOME meant that the gnome-panel started to leak memory by the hundreds of MBs, so now I'm back to KDE 3.5 on the work machine. I very much hope it won't be upgraded.
The features I'm using from KDE? There's a panel with taskbar, a workspace selector, konsole - and that's all, the same I used in KDE 1.