This was the first thing I thought of when I saw the iPad video :-)
I will definitely be getting one, because it will be so useful for work on the move, even WITHOUT any photo work, but having a cleverly-adapted PM would be very nice. Not sure how it would work, but there IS a way I know. Waiting to surprise us with its simple and obvious practicality.
I don't yet have an iPhone, but a fellow pro photographer is in the habit of showing off his best pics on one, and the iPad will be just that little bit better, without having the hassle of a laptop. (I have long given up dragging laptops around, and my Eepc netbook is incapable of anything much, except reducing me to a frustrated mass of red-hot fury, so that's back in its box these days. Awaiting techno-museum interest.