Using it first in satellites and medical devices indicates to me that reliability has been sufficiently demonstrated, but that cost is high. If it was cheap but unproven, you'd first see it in toy helicopters or something. I don't think it's unreasonable that a new technology could be demonstrated to be reliable but not yet be cheap.
Higher power density would be ideal for toy helicopters, as they typically have to use a different formulation of LiIon battery that compromises energy density and recharge cycle endurance in order to get a little bit more energy density.
