FWIW I have gone to LiFePO4 packs in all my planes. I use the Hyperion brand in the size that is best suited for my application. I use my Hyperion EOS061DUO to charge them (A123 setting). Superior voltage delivery even under high loads, negligible voltage loss between charges, no fire worries like lipos, robust cell design, and high capacity loading (mAh per ounce).
http://media.hyperion.hk/dn/fg3radio/
I buy all mine here:
http://www.rclipos.com/Hyperion_Receiver.htm
These packs are very popular now in the soaring community and we are having great results. I also have them in my pattern plane and a couple of sport planes and of course all my high end competition gliders.
I do have Eneloop packs as well that I use mostly in transmitters.
I have not used a NiCad pack in years and contrary to what Summerwind says I had superb results using NiMH cells for almost the last 20 years or so.
The attached graph shows a Hyperion LiFePO4 pack compared to an Eneloop pack. Both discharged at 500 mA load. Yes, the LiFePO4 packs drop off sharply near the end of the charge, but there is absolutely no reason to take them down that far. They can be charged at 4C, so after a set amount of time I simply recharge and I am good to go.