I used to buy excellent Maha rechargable batteries, but finally Energizer attracted my attention. Great price, great capacity. After about 20 recharges batteries are strong and do not show any signs of problems. I use them in old, power hungry and very demanding Olympus E-10 camera. It is known to draw up to one amper of current and to declare batteries empty as far as their voltage goes slightly below 1.2 volts. Considering number of pictures I can take comparing to Maha 2100 MAh batteries, I can say Energizer is very strong performer and 2500MAh is not just a number.
Some users complained about very bad performance for Energizer. There could be couple things to consider: - make sure you have decent charger: many high capacity NiMh batteries can be destroyed easily with cheap (<$20) charger - overheat and overcharge are usual suspects - some devices expect 1.5 volts, not 1.2 that all NiMh normally deliver; in general freshly charged good set of NiMh has voltage around 1.4 volts - but it goes down very fast to 1.2 v and stays there until batteries are nearly empty. Most modern cameras have "cut off" voltage set to 1.1 v
Update on Feb 7, 2007 I should mention that 4 out of my 12 Energizer batteries suddenly stopped to work. Surprisingly these are four spares I have not used much. I suspect that these batteries may develop a problem if left uncharged for prolonged period of time. For now I have bought Sanyo slow discharge Eneloop batteries (available at Amazon) as a replacement.