Finally, the MPX subsystem is included in the alpha version of Ubuntu 10.04. I was able to create three separate mouse pointers on my TabletPC as a test following this guide: http://alec.mooo.com/mpx.php
Why? Because I can ;) and because this is hopefully the beginning of multi-touch support throughout the Gnome Desktop environment.
Last night my wife and I shared the laptop for a while using both the bluetooth mouse and the internal trackpoint.