Unfortunately, we weren't able to attend the event in San Francisco yesterday, but our good friends at Joystiq were, and they've brought back this video of Need for Speed: Shift [iTunes link] and a few other games running on the iPad. Not only can you see how the accelerometer works (exactly the same as the iPhone, basically), but you can see how the regular iPhone apps will upscale to full screen (via what looks like a small "button" in the corner) on the iPad. Of course, this video isn't ideal, but it actually looks better than I thought.
Hopefully, of course, developers will actually put in the effort to recreate their apps for the iPad's bigger screen. That's exactly what the makers of Flight Control have said they plan to do; that game will be "re-imagined" to work on the iPad. They talk about not only making use of the bigger screen space, but actually going to the "next generation" of their games. It'll be very interesting to see, as the App Store evolves with the iPad, what kinds of markets emerge. Will we eventually have a set of games that works best on the iPhone, and a set that works better on the "big" screen?