I don't get the point fully. A larger tablet needs some sort of stand for viewing movies, or if you were using a wordprocesor of some kind on the full OS X version. But then what would support the tablet while you are typing on the screen and stop is sliding across the table? Do we have to have it flat on our laps?
I've been both excited about the tablet (having come from a Newton background) and similarly curious about the use cases being developed by Apple for this.
I still think a large enough screen can support full 'touch' typing on a virtual keyboard, and I think Jobs is dedicated to forcing the shift.
I'm going to go out on a limb and guess that there may be some sort of flip-out on the top-back that ramps the angle up just enough to allow comfortable viewing and simultaneous typing. I just played around with the angles with a piece of cardboard and my iPhone, and it really doesn't take much of an angle. Indeed there have been desks with built-in surface monitors for a long time. Perpendicular to the desk isn't necessary.
I've been using Layers on my iPhone for a while now and can't wait to get a really good painting/drawing program on a decent size screen.
I can see it for music and performance use as well.
I just think that folks are thinking inside the box here, and insisting that it has to 'replace' a desktop or laptop. I don't think that's the purpose.