Aside from slowness mark mentions and some impenetrable (to me) new desktop metaphors (like no desktop) they just decided not to carry over "old" things like an auto-hiding task bar and tons of other familiar KDE elements. I used to be able to set my background to a "update-every-5-minute" webcam grab. Gone now. or I can't find it.

The explanations seem to vary from "You don't need those things anymore!" to "this is a development release!" to "You don't need those things anymore!" to "Maybe we'll have some of those things in 4.2."

So I have set up Fedora 9 in a virtual machine, turned on rawhide, and I run yum update every few weeks to see if I detect any KDE4 miracle.