None of these is particularly problematic. It ain't rocket science to use hydrogen with minimal leakage--it has been done successfully for years. From a reactivity standpoint, hydrogen is less dangerous than gasoline (hydrogen has a wider explosive range and lower ignition temp, but because of its high permeation rate and low density, it is less likely to accumulate to within those explosive limits). Transportation over long distances can be done in existing natural gas pipeline infrastructure.
"Transportation over long distances can be done in existing natural gas pipeline infrastructure."
That isn't true, it would require an upgrade to the pipe.
I think that all of the problems mentioned ARE significant. The H2 molecule is very small and VERY LIGHT, which means that the average velocity of the free molecule is higher than that of any other gas at any temperature. It will escape where no other gas will. The natural gas distribution system actually does have a considerable amount of leakage. I discovered one such leak a block from my house a couple of years ago, when I saw bubbles in a puddle after a rain. The actual leak was in a distribution pipe about 15 feet away from the puddle. Actual distribution losses in the US amount to billions of MCF annually. If it were hydrogen, expect that number would multiply several times IF it were used the same way - a BAD idea.
You note the greater explosive range, but omit that it is not trivially greater but is several times the next gas on the list. Also, the flame is invisible and unquenchable as long as hydrogen and oxygen are both available, over that very wide mixture range.
Distributing a gaseous fuel is very different from a liquid. First of all, how do you measure it? Liquid is easy - just measure the volume, or measure the weight. Residential gas meters operate at a fixed pressure, over a relatively small temperature range.
But H2 fuel would have to be very highly pressurized if sold as a gas. Maybe you can measure the volume, temperature, and pressure, but they could change during a fill - it could get complicated. Weight? The container will be MUCH heavier than the contents, and measuring the change in weight with enough precision would be difficult. Will it be distributed at low pressure (60PSI, like residential service) and compressed at the delivery station? That's pretty energy intensive in itself. Delivery by truck means either transfer or container exchange - and again, transfer would take a lot of energy. Vehicle tank exchange and refill might be the most economical way to distribute H2.
Free hydrogen will ALWAYS be a derivative product on this planet, and will always require more energy to produce - by several times - that its fuel energy content. That makes its production and distribution an energy sink, not a source like petroleum and natural gas. And it means that it has value as an energy vector only as a transportation fuel and a few other special circumstances. Homes can be heated at lower cost and higher efficiency with the electricity that would be used to generate the hydrogen, particularly if it runs a heat pump.
Transportation is a different story, since low weight and high energy density are the most important characteristics of the vehicle fuel, whether ground or air.
We SHOULD be moving to hybrids for all of out ground transportation, but for more reasons than immediately apparent. Already, a major sector of our commercial transport is hybrid powered, in the form of the diesel-electric locomotive. If the railroads had an electric trolley or underground slot pickup for electricity, we would need only a small increase in electric generation capacity to eliminate all of that fuel use.
And if we could find a way to power our personal vehicles from the grid - at least in city center and major intercity routes - we could really tell the Arabs to start making windows out of their sand, because we would not need the only other thing they produce.
It is possible that such an electrical distribution system for vehicles could be an easier problem to solve than distributing gaseous hydrogen.
Actually, we already have a high-volume distribution system for one of the most hydrogen-dense liquids that exists - gasoline! The light hydrocarbons contain almost half again as much hydrogen as water, and the hydrogen can be released in an exothermic reaction, unlike any other source. Maybe "regular or high-test" will refer to Octane or Propane in the future.