Not virtual desktops and not just terminal windows.
Virtual consoles/terminals.
For example, in Slackware (my fav. Linux distro) I can ALT-F1...ALT-Fx (where ALT-F7 is reserved for X) and get an entirely new text login screen (much like how things look in single-user mode on OS X). I can also configure (with some work) more than one graphical login.
In Linux having multiple consoles is handy so that if, for example, X locks up and you can't kill the X server in that session (ALT-Backspace) you can switch to another console, login, and kill the actual X server process with "kill." It could be handy running two graphical logins if say, you use one for the main user, and one for root (though I wouldn't suggest this in any kind of real environment--home is OK).
Anyway, that's what I was asking about.
Any other ideas?
Kent!
edit: terminology