Re:Switch User functionality (Score 5, Informative)

This is already available in Linux:

• hit ctrl-alt-F[1-6] to get out of the current X session to a virtual terminal
• login with other user
• xinit -- :1

Now you have two completely separate X sessions running at the same time. I've no idea if there's a point-and-click (x|k|g)dm way to do this, but the capability is there.