For instance, in Gnome, I can set up multiple Gnome workspaces. But when I add a second monitor, all I get is my current workspace extended onto the second monitor. I hate it. Every time I run a full screen application I lose the second monitor, and have to go re-enable the stretched desktop after I close the application.
Also, I don't want separate X servers. I want to be able to move windows between workspaces. Also, it would be nice to be able to switch workspaces independently on each monitor.
Is there a window manager that has this kind of functionality? I'm surprised Compiz doesn't do it. They have the desktop cube. Switching workspaces independently only seems natural in that case.