Certainly technology to handle hydrogen has advanced since the days of the Hindenburg. Is this a viable option now? Also, I was wondering what those engineering uses of helium are that would not also work with Argon?

I always thought that the only 'smart' application in an H2 economy would be flying. I would imagine very large Zeppelins circling the planet on fixed routes in high altitudes; never landing, always at full speed, being accessed by smaller shuttles carrying passengers and cargo from and to the ground. Solar energy would be the propellant and collected from the cloudless sky via a thin film PV skin. H2 would provide buoyancy and at the same time serve as energy carrier for day and night operation. Traveling above 300km/h would provide additional lift and controllability. The longer travel times would be compensated by comfort and convenience known from large cruise ships. I would be the first to use such an infrastructure for my long distance traveling! r

PS: whenever I have the opportunity I visit the Zeppelin museum in Friederichshafen just across the lake - and I'm always fascinated walking around in the 1:1 model of the Hindenburg (http://www.zeppelin-museum.de/Text_TuK.htm)