Every critical analysis of hydrogen combustion or fuel-cell use in cars has made the mistake (IMO) of placing a fossil-fuel energy source-well at the base of the calculations. Some of these studies have been revealed to have been funded by... *gasp* fossil fuel companies.
In just the last decade, hydrogen efficiency from grid-to-motor has been climbing rapidly. I would never argue that we could go to a hydrogen economy tomorrow and realize a reduction in pollution and eliminate a dependancy on fossil fuels. I would argue, however, that the technology has already demonstrated remarkable potential; enough to entice every major car maker to start building fuel-cell cars and trucks. I would also argue that we could advance the technology in a dramatic fashion by declaring it a national goal (like landing on the moon) and investing substantial federal money - you could even legitimately claim that we should use national security funding since we're talking about reducing or eliminating the need for us to be in some volatile parts of the world.
We were just talking the other day here at work about how inspirational the goal to get to the moon was for the country. How every person who's job had some tie to it - be it the accountant working for the company than made the micro-switches - felt like part of the program. Wouldn't that be inspiring to see us stand up to a challenge like that as a country ... might just breath life into our automakers in the distant future too.