Personally i like KDE4 very much.
I think it was released too early though.
KDE 4.0 and 4.1 were not exactly stable, and many KDE apps were not yet ported to KDE4 (KDevelop!).
However since KDE 4.1.2 thing went very well.
KDE 4 is my desktop of choice, it's useful, pretty and innovative.
I'm waiting to start using KDE 4.2 soon