I have been using NiMH AAs for some time now in steadily increasing mAh ratings. The last batch I bought are rated at 2700 mAh. They all have worked fine but I sometimes forget to throw them in the charger the day before a shoot and end up having to swap out batteries due to the self discharge characteristics. Somewhere in one of the Strobist related sites I found a reference to a new type of NiMH that holds its charge longer. They are made by Rayovac and are called Hybrid NiMH. The only place I have found them is Walmart. If memory serves they cost $9 for a pack of 4. The mAh rating is 2100 but because they hold a charge so much better than standard NiMH they seem to last longer. That, of course, is more because of my failure to charge up the regular ones when I ought to but the point remains. In other words, good batteries for the memory challenged.