The general consensus is if its going to be driven on the road more than the trail, air shocks are not that good. Apparently they heat up very very easily with extended cycles. You see them a lot on rock crawlers because they move so slow. As for charging, I think that they have a schrader valve and you can charge them if you have the right kind of air. I swear Ive seen pictures of someone charging one with an on board air compressor. It was either that or he had a tank of whatever they tank sitting in the truck.
Some good reading:
Im about 95% certain my next truck will be a Scrambler and I will be linked and running coilovers. When you get ready to buy, call Poly Performance. Theyve got great prices and they all race and drive buggies and trail toys and can tell you what spring rates and heights would work with your set up.