Ever play a 3D hand held game tied to a gorgeous blond model? Yeah, it happens all the time, so boring. But the video does give a nice look at the 3D aspect of the system. In the video you can see how it adapts to the players movement of the device.
Here is another 3DS Video of Metal Gear Soldid - Snake Eater:
And here is a 3D game released for the original DS out right now in Japan:
It uses the camera to track the player and uses that information to adjust accordingly. If you import the game, you'll have a nice preview of what the Nintendo 3DS will feel like.