I just installed YDL 4.0.1 on a G5 Xserve and everything went reasonably smoothly, except it's stuck on 640x480 resolution. If I switch to the monitor's native resolution (1280x1024) then X won't start up and I have to restore /etc/X11/XF86Config to get things working again.
I could just about live with 640x480 if I had to, but I can't get at the buttons on some of the windows in KDevelop, so I have to find a solution for this.