I am a long-time KDE user, and always enjoyed the high functionality and pretty good UI performance of KDE3/QT3.
Since KDE-4.0.1 I try KDE4 based distributions from time to time, and I am quite unhappy.
What really hurts is that QT4's window-redrawing is as slow as GTK's, maybe even slower - even if trolltech advertises it as x-times faster.
Furthermore it seems design and eye-candy has (had?) higher priority than functionality - a lot of common stuff is not implemented or doesn't work as expected. They even maintain their own HTML engine, but are not able to get the basic desktop right.
KDE-3.5 is phased out by many distributions, so I'll have a look at Gnome. However I hope the gnome project will go different ways than its founder and innovate instead of just cloning others technologies.
After so many harsh words, I would like to say thanks to all who made linux on desktop reality. My discomfort with KDE4 is only caused by the high standards (your work) I've become used to in the past.