No, but it does open up user interface possibilities. Think about desktop GUIs. Given an object on screen and a single button mouse, your vocabulary for interacting with that object is limited to: single click, multiple (double, triple) clicks, and drags. You can add gestures if you're really adventurous.
Adding a second mouse button instantly doubles your vocabulary, plus a little more if you're up to getting down with both buttons at once. More buttons increase the interaction possiblities further, though eventually you'll wind up with a keyboard, just one with a nifty light on the bottom. The returns diminish to nothing long before then anyhow. Right now, the Internet tablets are pretty much at the one button mouse level of interaction. There's some pressure data, but it's of such a small range, and so unreliable, that it's not even used to determine what keyboard pops up anymore.
So we're where Mac users used to be. Where Mac users used to be made fun of for being. Heck, with double-taps being awkward and unreliable, we may not be even that far. Shh, don't tell!
Multitouch would certainly expand the vocabulary of the tablet UI. So would having a powered stylus that charges in its silo and sports one or two buttons on its side, but those are a pain.