The only thing I can see with hydrogen is the price. Wouldn't it be more expensive than gas?
That depends. How expensive is gas? You can make hydrogen by arcing a huge electrical current across a bucket of water - the water is pretty cheap, but the electrical current required is like running your house for a month. The other way to get hydrogen is to pull it out of natural gas the same way you pull gasoline out of oil.
In case you don't know, here's how gasoline is made. First you have to find crude oil, and usually it is in a crack deep underground, so you have to drill down to get it. In the case of offshore oil, sometimes the place you have to drill is under 1000m of water. After it comes up, it goes to the refinery. What the refinery does is heat the crude until it becomes unstable, which is called cracking. Depending on how much you heat it, you get different products - kerosene, lube oil, gasoline, butane, propane, etc. How much does this cost? Hard to say. Use this equation if you want a rough estimate:
($/gal gasoline) - (taxes&profit) * 42 = ($/barrel crude oil) + (refinery costs)
1 barrel = 42 gallons
It seems like the refinery costs would be a lot, but since they already exist, and they do so much volume, they basically become zero, so the current cost of gasoline is based largely on the price of crude oil.
If you make your hydrogen from natural gas, it should be just as easy as making gasoline from oil, since its the same process. And the US has huge natural gas reserves, with more to be found all the time. Actually, natural gas occurs right alongside the oil, and we usually just flare it off because its value is so low. Imagine that - a great energy source being thrown away because only the oil matters. That kind of logic is why high gas prices were such a good thing.