I am not a fan of air compressors. I could be biased though, as my dad has a compressor that is older (and louder) than me, yet it can barely power the few crappy air tools we have. Suffice to say, I get more torque out of my socket wrench than the air wrench.
But compressed air can also be used for propulsion. I've seen some designs for air cars, but ultimately all the weight of an enclosed vehicle means a lot of short cuts need to be taken just to get it up to bicycle speed. But what about say, a motorcycle? Two Indian scientists have put forth a design in the Journal of Renewable and Sustainable Energy for a compressed air motorcycle. Me thinks they are on to something.