The current Forbes anniversary issue includes a series of articles on 85 Innovations That Changed The Way We Live. Of note is the article on Larry Burns, the fellow heading up GM's hydrogen car efforts.
The chassis, which GM calls the "skateboard," is supposed to last for decades, and it can put on different bodies like they were clothes. You might have a minivan body for Saturday afternoon and a sports car body for Saturday night. The idea is to be able to download different driving characteristics into the software that runs the motors and the suspensions, making the ride edgy and quick, or boatlike and soft. When a car is sitting in the garage, its fuel cells could supply the power needed to run a house--maybe even sell electricity back to the grid.