Are there any unbiased, layman-friendly explanations of the challenges kicking around?
Aside from "Alternative Energy without the hot air" you mean?
Issues with H2 fuel cell cars.
1)They are not fuels, they are energy carriers, storing the energy generated elsewhere.
2) What kind? The LH2 at -253c or the GH2 at 10 000psi? BTW the USAF (who deal with quite a lot of pressure vessels, like the one that destroyed the AMOS 6 satellite on the F9 a while back), rate them by "lbs of TNT equivalent." and 10Ksi is toward the high end of such tanks.). There is a (relatively) low pressure system using metal alloys that absor/desorb GH2 but people seem to think it's heavy. Google "Interstitial hydrides."
3) A US study reckoned the diffusion and embrittlement issues are containable (so to speak) with suitable alloys. But you're looking at a whole new distro network with (ideally) all welded joints. LH2 normally uses "Vacuum Jacked Line," which is double skinned piping with an evacuated cavity between. It's a PITA to use and mfg.
4)We know how to do bulk storage of gases (really large scale) much better than store electricity.
But I'm not unbiased. Hydrogen is the physicists choice for a fuel. Not an engineers choice. IMHO
Fuel cells ¬ stupid.
Fuel cells with H2 (on Earth) very stupid.
My alternate fuel choice is the sugar solution fuel cell.
Room temp storable liquid.
Compatible wit existing supply chain .
Very safe to handle (unless there are bees or wasps around)
Renewable.
Sustainable.