I am using a set (4 pieces) of Energizer 2500mah with a Energizer 15 minute charger. I initially had problems with it charging but after my 2nd or third use, I had no problems with it.

My main uses for the batteries are:
- digital camera. (does more than 300 shots w/ flash)
- battery powered cellphone charger. (extends the power of my N80, especially when I am using it as a MP3 player on long trips like on the airplane)