I've been using these new nickel-zinc AA cells for about 2 months now. I'm impressed by how long they will power things compared to the usual NiMh cells.
I have a Magellan GPS unit that uses 2 AA's. It was probably designed for alkaline cells. New alkaline cells give a full scale battery bargraph, but freshly charged NiMh cells only make the bargraph hit about 80%. NiMh cells drop to about half scale after an hour. I only get about 4 hours with NiMh cells before the voltage drops too low and it turns itself off. Alkalines will last about 7 hours. The new PowerGenix NiZn cells give a full scale battery bargraph for about 3-1/2 hours, then it slowly drops until the unit turns off. My first test powered the GPS for 6 hours and 20 minutes, the second time it went 6 hours and 55 minutes. I left the batteries in the charger longer the second time I charged them, about 4 hours instead of 2. With my GPS, the PowerGenix AA's lasted almost twice as long as 2200mAh NiMh.
I have also used these in my Fuji digital camera that uses 2 AA's. They also last a long time, longer than the NiMh cells I have used in the past. The LCD display is also just a little brighter with the NiZn cells.
I have a little Grundig G6 radio that also uses 2 AA's. It won't turn on with these installed. I'm guessing that the radio is sensing the higher than usual voltage (about 3.6 volts) and won't power up. This is the only device I have found so far that isn't happy with the NiZn cells.
When these come out of the charger, they read about 1.82 volts without a load using my Fluke DMM. Of course the voltage will drop when current is drawn and as the battery discharges.
To sum it up, these cells act a lot more like alkaline cells with the higher voltage available. It takes a lot longer for the voltage to drop down to about 1.2 volts per cell when comparing to NiMh types. These start off at a higher voltage than alkaline and take a good long time to drop to the point when you need to recharge.
Give these a try, I think you'll be happy. I'll be buying more AA's and some of the AAA size when they are available.