Do fuel cells hold a formidable advantage over liquid hydrogen kept at harsh below freezing temperatures ?

Fuel cell technology being developed by several automakers, namely Honda and Chevy, is a non-combustion form of energy unlike liquid hydrogen which essentially uses the same engine structure as conventional cars. This require liquid hydrogen to be kept in the vehicle at 420 degrees below zero which is costly. In fuel cells, hydrogen based cells are kept on stacks. A hydrogen – oxygen reaction creates electricity that powers the car. The fuel cells are refilled with the hydrogen chemical.

will the hydrogen fuel cell vehicle ever hit mainstream? if so, when will they become commercially available?

is a concerted effort being made to push through development of a car that emits WATER as it's waste product? Wouldn't this solve alot of problems if it were widely used? how stable is using hydrogen as a fuel source? I keep seeing glimpses of commercials and reading snipets of info on such a vehicle, but do you think it will ever become a functional reality?