I purchased a Surface Pro tablet to be able to use it as a portable Cintiq tablet. I own a Cintiq 21ux and use it with Ubuntu.
I was kinda disappointed after installing Ubuntu since pen pressure sensitivity did not work.
I poked around and realized that Microsoft shipped a wacom driver compatible device but changed the vendor and device id.
I wrote a script to use the wacom drivers and calibrate the stylus and eraser:
fix-surface-pro-pen.sh
I'll try to add my changes to the wacom drivers to avoid having to do this hack if I get some time.