Just twittered about that, basically I don't think we would master multi finger interaction.. I think using keyboards and guestures is different because each is static, the keys are always in one place, and the guesture is always one general shape with my fingers + an action..
Interaction is much more different, we need to focus visual attention to that point, which is why the mouse works well, because we focus on one thing, and synchronize our hand movements to that.. I'm pretty sure that humans cannot focus on multiple things and coordinate fingers at the same time..
Which then makes me ask, whats the advantage? I've lost a mouse (which is really more accurate than a fat finger), and if I haven't lost the mouse then why they hell would I use the touch surface?
There are places where touch really makes sense, and I don't think Microsoft essentially added touch to win7 so much because they envisioned us all touching our screens and the mouse dying.