I installed KDE4 in Ubuntu (my desktop, not my laptop!). It took some time for Kubuntu to catch up to use KDE 4. A simple “sudo apt-get install kde4” didn’t work so well. I got the install going and up and running. So far, there isn’t a whole lot going on. It’s a usable desktop which utilizes the KDE 3 applications. It is resource intensive and my older desktop doesn’t work very well with it. For now, in my experience, the stability lacks something and so KDE 3 will continue to suffice.
For Ubuntu, another option happens to be XFce. I’m impressed. There is no repo way to get this for Fedora or I might be using it.
I’ve had some stability issues in F8 with KDE. This almost always occurs when I’m running MATLAB (no shock). The KDE panel crashes on me inexplicably and I cannot get it back without logging out and then back in. I attempted the use of Fluxbox again for a few days. While I really enjoy it, I kept struggling with it’s stability as well (a first!). I have gone back to KDE 3.5.8 for F8 for the meanwhile. The instabilities I see here are less than those I see in Fluxbox.