I've got a battery pack in my TX and one in my heli... both are made from Ray-O-Vac 1800 mAh AA NiMh cells. They are a bit havier than the NiCd 700's... take the exact same space though.

Its fairly safe to charge them on the radio's original wall-wart, C/36 rate is almost a maintenance trickle, but I can't safely leave them on beyond full charge. (for the 3200's it would be C/64.... or 3 days to charge it. you could leave it 72 hours safely starting from a partial charge.) The NiMh peak detecting chargers are getting inexpensive. (even the Li-Ion chatrgers are comming down)