I've got a Dell multi touch (21.5 inch) to play with since last year.. and it didn't work well with Win 7.
1. With Win 7, the touch did not translate well into mouse movement. Fader movement is accelerated, hard to control. With the step sequencer, touch-hold did not engage the delete note function (mouse right click). The patch will probably address these issues.
...but even if the patch for Win 8 works..
2. For the current X2 screen, 21.5 inch monitor is too small to move the console fader with any accuracy. Part of your finger will cover the fader, making it hard to see the movement. A really big monitor might help. Also, there is this slight delay moving the fader by touch, where as with the mouse wheel, it's immediate.
Then you have the problem where to place the touch screen.. as pointed by many here, placing it at regular position, your arm get tired soon.
@21.5 inch, the monitor is small enough to be placed flat or at a low table..but with small faders problem. Big monitor will be hard to be placed flat.
Perhaps a feature to make the fader bigger is good. I have suggested a feature request for this.
It may be just a feature to be compatible with Win 8, but I won't be practical to use.