I think that's a clever idea. I'm inclined to agree with the majority that it probably isn't something I would want, but I would be interested in trying it out before I passed judgment. The Trackpoint would be the main competition, and it would be hard to beat.
I would not want a printer built in. It would add size, weight, and cost for something I do not need. I've pretty well stopped using paper, both at home and at work. I print something maybe once every couple of months.