Explosions dont hurt soilders flying in the level above. Ive tried taking screens but they wont come out right. Go try it yourself toss a nade under your guy while your in the air. Also wont detenate proxys by flying over them. Flying Suits > Power armor for that, the h2h advantage, and the added mobility and armor (every little bit helps). Dont forget the rooms in the alien bases that are two story. Its worth vrs elerium use depends on how desperately you need elerium for other things, but I think its worth it.
k:
I have the windows version, dont know if it differs from the dos version about the nades.