I liked KDE 3.5, as implemented in Mandriva. I tried kubuntu (with KDE 3.5) and found it was a bit like the poor cousin to ubuntu. So back to Mandriva I went. Then they went KDE 4 and that was awful, so went back to gnome on Ubuntu 9.10. I'll stick with this as long as I can- about 1 mth LOL.
I don't know what it is about gnome and kde 4 but both these GUI's just feel sticky, with little delays on every menu that drops down, every gadget I click.
TBH, I'm over the endless cycle of OS re-installs with Linux. Its just a fricken 'puter these days.