I have integrated Ubuntu Jaunty, Mac Tiger, Windows XP, and a MythTV PVR into my desktop environment using the default compiz in the Ubuntu repositories. Ubuntu is the host operating system, Mac Tiger is a VNC connection on the local network maximized to fullscreen, Windows XP is running in VirtualBox, and MythTV is capturing HD 720P via FireWire from my SA4250HD Optimum cablebox.
The cube also looks nice with these multiple screen, and with a powerful video card you can actually see MythtTV while on the cube. Open /usr/bin/mythtvfrontend and remove the line at the top that prevents it from opening multiple instances. Now you can open a MythTV frontend on each of the cubes viewports. You can actually watch different videos on each side of the cube.