Imaging Resource battery shootout
Kudos to Dave Etchells for posting an excellent (technical and logical) comparison of different brands of high capacity AA NiMH batteries. His comparison (although done outside of a digital camera) measured precisely the amount of power these batteries are able to store and return. "First, I was rather surprised that the Rayovac battery / charger combination did as well as it did. Besides their being a newcomer to the NiMH world, I'd seen rather disappointing results from other "name brand" batteries, namely the Energizer Accu Rechargeables."
It's also worth noting that even four of the very best AA NiMH batteries from Dave's test can still only provide 6.7 Wh of power (although are rated at 7.7 Wh). Where as the best Lithium-Ion packs around (Canon's BP-511/512 and Sony's NP-FM50) can deliver well in excess of 8 Wh.