I have no problems with k3b 1.0.1 (the package in Testing) in 5.8 Standard.
So far as I remember, no problems with 1.0 either.
Strangely enough, there is no .desktop file in /usr/share/apllications, but the icon still shows up in the menu.
It didn't show up right away after installation, it took a while, but it's there now. So I guess xfce is getting the .dekstop file and the icon from somewhere else.
Also, I'm able to launch both k3b and amarok from the command line. /opt/kde/bin is in my PATH in .bashrc, though I didn't put it there. It just showed up. (the kdelibs package I installed was also the one in testing)