The biggest problem with hydrogen is a "chicken and the egg" one.
You don't want a hydrogen car, because you don't have a hydrogen filling station on your block. There's no hydrogen filling station on your block, because there aren't enough hydrogen cars in the neighborhood to warrant one.
Here in NY, a
http://www.nytimes.com/1984/09/02/nyregion/law-requiring-gas-stations-to-have-air-pumps-in-effect.html">law was passed in 1984 that any gas station with 4 or more pumps needed to have an air pump as well (for filling tires) the pump could be free, or it could be "coin operated," but it needed to be there.
A similar law
could be written to require a hydrogen filling station at gasoline stations of a certain size or larger. (If they've got water and electricity, they can
http://en.wikipedia.org/wiki/Hydrogen_production">produce hydrogen. Or, they
could "reform" gasoline.)
A hydrogen generation/storage facility would be more expensive than an air pump, but that could be subsidized in part, or in full.
That would put the egg in place.