I don't think it would take much effort at all before you'd rarely have to actually look down and see what you were doing.
I also think that we'd have to keep an interface, but it could be more like OS X's menu (Or like how he changed things in world wind).
You would still need to have menus for some things, but for the most part you could remove a lot of the menus.
I also liked the idea of having a virtual keyboard. You could program up different varieties of keyboards (No more QWERTY vs Dvorak). You could have one for programming C/Python/Whatever where you could have common features inserted just like you were typing. (Yes you can do this with programmable keys, but not per application with visuals).
I think, depending on what it's like to tap on a screen all day. His would be great. And I can't wait to see it evolve and go into production.
For 95% of what I do this is just as good or better. And I am sure for another 4.8% of that you could think of ways to make it work. And the rest of the time, you can always have a bluetooth wireless mouse and keyboard at the ready hidden away.
Bring on the screens!