It's good if you don't care about volume, but care about weight, such as if you are trying to go into space. It takes an incredible amount of energy to break free from earth's gravity, and every gram of fuel you have you also have to lift off the ground.
It's terrible if you are concerned about volume, like if you have to fill a terrestrial vehicle.
Hydrogen has other problems that prevent it from being used seriously as a fuel that canibineer pointed out.
If you really want to make hydrogen useful so that it is stable for transport, has high energy density, and will be safe for use by the common man you should bond it to a long chain of carbons. But then why not just skip all that and use gasoline directly?