I wanted to check how many simultaneous touches the iPad's screen supported, so I wrote some code to test it. Turns out that it supports eleven (11) simultaneous touches (the 12th won't register at all - I had to enlist Lauren's help to test that).
So, it really is an all-ten-fingers device, if you need that kind of input resolution. It also handles the visual touch-tracking pretty well, considering I didn't really try to optimise it at all. Each touch is shown by a small UIView, and the axial markers are drawn by the underlying primary view. Trivial, but kind of fun.
If you want to grab the source code, you can do so here: http://mattgemmell.com/2010/05/09/ipad-multi-touch