Hot-swapping different user GUIs under Linux

I read that Windows XP has a "new" feature that lets users hot-swap their desktops. Instead of logging out, a user can put his session into the background and another user can log in. This is of course very useful if you are downloading large files or running services and you don't want to interrupt the process. If figured out that Linux is able to do the same already for years:

When I have a process with a GUI running in GNOME (or KDE; let's say lmule) and another user wants to access his account using GNOME and I don't want to terminate my own GUI session, I switch to another (virtual) terminal via Ctrl-Alt-F2 and the other user logs in and starts an x session ("startx -- :1"). Using RedHat 9, the new x session started from F2 is initially accessible via both consoles (F2 and F8).

When the other user has finished his work, I can without problems go back to my GNOME with Ctrl-Alt-F7 and resume whatever I have been doing under GNOME.

However, when the other user wants to access again his x session, it can only be accessed via Ctrl-Alt-F8. When switching to the F2 console one might get the impression that X has crashed (which is not the case).

If the Ctrl-Alt-Fx combination doesn't work, you have selected a wrong keyboard layout (one that is not meant for x windows sessions, but for a command line terminal). You can switch to correct terminal via the GNOME keyboard layout switcher. The GNOME keyboard layout switcher is an applet that you can add to your panel (click the panel in an empty area, add to panel, utility, keyboard layout switcher). To choose a correct keyboard layout right-click the keyboard layout switcher icon in the panel, Preferences, Add. When you click the triangle in front of the different languages and then the triangle in front of the country, you sometimes see two different options (in my case: Finnish keymap and Finnish xkb keymap). You should choose the xkb keymap, otherwise Ctrl-Alt-Fx won't work.