The A123 cells have great potential. I don't think they will catch on in PA models just yet because they have a lower energy density than Lipo's (we look for any advantage we can get). They are however a good lower cost (about $90 for 10 cells) and safer (aluminum case rather than foil bag) alternative to Lipo's. There is no reason they can't be used in lower skill level events or sport flying. To give you an idea of performance, they are better than NiMH, but not as good as Lipo's.
One drawback is the need for a separate charger. A Lipo charger will not charge A123 cells because of the voltage difference, 3.6 volts for the A123 cell and 4.2 volts for a Lipo cell. For this reason we will also need different pack configurations. A123 cells have a capacity of 2300mah ONLY and a weight of ~2.5oz ONLY. Lipo's on the other hand have MANY capacities and weights to choose from.
If you feel up to the task you can modify your Astro Flight 109 charger to charge A123 cells (thanks to Pat Mackenzie). The mods are very simple and only require a capacitor, wire and a spdt on/on switch (oh yea, and the risk of voiding your warranty or ruining your charger). Once you are able to charge them they can be charged at greater than 1C
, so flight to flight turn around will no longer be ~ 1 hour like Lipo's.
I think A123 cells have a bright future (or new batteries that are developed from their technology). I would like to use A123 cells and see what the highest attainable performance is and stay on a tight budget. I have thought about using NiMH cells again at some point, just to see what can be done for cheap.
At any rate I am keeping an eye on them.
Emoli cells are another alternative not talked about.