A123 batteries were supposed to be the next big thing, but then development on them just fizzled. I think there was a problem with A123racing which was the company that made them to begin with. Lipos have caught up to A123 batteries for charge rate and discharge, and given the much greater variety of lipos they are still the best choice for powering electric models. I use 2 cell Lifes for my receiver packs, but I think it'll take a fair amount of development before A123 or Life batteries knock Lipos off their pedestal.