here's the BIG problem with hydrogen fuel cells. You get less energy out, that the energy required to generate the energy in the first place. *
The only way hydrogen power would ever be viable is if nuclear power was used to generate the energy for storage in a fuel cell, but thanks to the green lobby and misconceptions about nuclear power (i.e. chernobyl and 3 mile island) this will never happen.

*that and hydrogen is damn well dangerous stuff.