Just to let you know: I've been following the news about KDE 4. As uelsk8s said, it's unusable right now. Nevertheless, the KDE people are working on adding more features to bring it to the point where it's as spiffy as KDE 3.5.x. Apparently the problem is that they needed to release version 4 in order to get input from developers and users about bugs and whatnot, so they released it even though it's not really ready for general use. My guess is that six months or so from now it will be much more usable.