I compleatly buy this argument about human/computer interaction, regarding UI and mutli-touch interfaces ala the iPhone.
I have to say that ergonomics both on this, and a more specific level (like keyboard layouts, and command line conventions) are of a great interest to me.
I have to say though, that being able to do something more multi-touchy with a track pad would be nice. We'll remember that we already have the two finger scrolling, which I can't really live with out, so having an additional command ability (like a second mouse click.)
Frankly though, the major coup of the iPhone is the pinch and zoom thing, which makes a lot of sense on a very small screen, but signifigantly less sense on your MacPro Cinema display, or MacBook.