I think one of the things people have got wrong about it is the importance of the power source: Kamen's Stirling engine would be very cool, since it would probably be a multi-fuel/flexible-fuel engine. Out of fuel at a party? Get home on a few shots of cheap brandy. The hydrogen hype is just that. It might be an OK way to store eletric power (water to hydrogen and back to water), but it will not be revolutionary to the economy without a coresponding revolution in cheaper nuclear power plants - and that would take a decade or more to build even on a crash program.
Also, a scooter is just a probable evolution of his wheelchair. Who knows what the optimal package will be? A semi-enclosed motorcycle, like the thing BMW has been playing with? A recumbent fully enclosed commuter motorcycle? One that could seat two friendly people? Highway speed capable? The factory is not small, but nor is it anywhere near the same level of investment required by a new car coming on line. The game will be won or lost in the steps following the first product.
A multi-fuel/flexible-fuel engine would be revolutionary, especially if it could run on water. Even if it got 1 mpg that would be far cheaper than gasoline and it wouldn't even require a refined product. If you ran out of fuel you wouldn't need anything but a pond to refuel. I still don't understand the hype over the scooter part unless it was a poorly written article by a technically illiterate journalist that didn't understand the implications of the power source.