I think KDE4 is great, but there's some things which need to be done (in my opinion, of course).
1) First of all is the size of the taskbar. It's really too big.
2) The second thing is config panel. After KDE3.5's one, KDE4's is really poor.
3) It's nice that there're wigets in KDE4, but some of them are useless. For example: i prefer analog clocks to digital ones, so i can use that wiget. But for what - i have very BIG digital clock on the taskbar. It's not about all wigets - there're very useful things like Kget.
And i have some problems when logging out, but it may be my comp's own bug
That's all that i can say for that moment. Sorry for my english (i think there're some mistakes :rolleyes