Lower spark energy Broader range of combustibility Faster detonation speed (? [1])
It's only positive is it dissipated quickly, but that's not that great because it goes boom boom at 5% H2 -air. Everyone I know who has worked on combustion problems (I haven't myself, but colleagues have) give H2 a lot of respect.
[1] this one is an educated guess on my part based on the thermo.
