Months ago I tried to get this working and gave up as it is more eye candy than a needed function. Well, it is working now and to set it up there are a couple simple things you need to do.
First of course is install it and make sure you have the right video drivers for your system or it won't work. Before you activate it go to Compiz Settings Manager and enable Window Decoration, Move Windows, Resize Windows, Desktop Cube and Rotate Cube. Be sure you install the Compiz Fusion Icon which you can run and it will show up in the tray so you can turn it on and off at will (Right Click>Select Window Manager, either Compiz or Kwin. Also on that Icon you can select the Window Decorator (either KDE4 or GTK). My friend has to use GTK or the title bars are messed up. We don't know why yet but he has Intel graphics and I have ATI.
Window Decoration, Move Windows, and Resize Windows are not enabled when you install it so you will have no title bars and can't move or resize windows. I don't know why but they aren't so enable those first! Also, there is a bug or two. If you rotate the cube when it stops it will flash the desktop and the pager does not work right. You can get the pager to work by fiddling with the settings but if you log out and back in you have to fix it again. I don't know a fix for the screen flash yet.
If you have a ATI/AMD video card enable Workarounds and check the fglrx fix to fix menus that are slow/invisible etc. There are other fixes in there but I have ATI so have at it Nvidia/Intel guys. Hope you get it going.
To rotate the Cube hold CTRL and ALT then hold the left mouse button and spin away!