I got a LaZa Cell extended battery for about $20 and it basically doubles the capacity of the stock battery. I've been using it for pretty much a year now and it still holds a full charge and everything. I remember my phone pretty much "accepted" it right away and it read the percentages right since I first installed it. I like it, I never had any problems with it, so I would recommend it. I haven't tried any other ones, so I can't compare thought.