I've so far stuck to KDE 3.5.9, but 4.1 seemed quite usable when I got to
test it (4.0 was just horrible).
Really the biggest incentive I had to move away from KDE (which I didn't
do) was that basically there was no usable KDE that was maintained.
Especially Konqueror 3.5.9 bugs were just closed since "we don't support
it any more", while KDE 4.0 was such a mess that I'd rather live with
Konqueror crashing on certain pages than try to use it.
Well, if Gnome hasn't become much better since I last tested it, I still
think KDE 3.5.9 was by far the best option there was (and yes, I know
about xfce & the simpler window managers).