I got the Mugen 3600; as with almost all my battery purchases, it worked perfectly. The only one I've had any problem with is from this company called... I don't know, oh, Nokia. I've removed the Nokia battery and the others all work fine.

The bulkiness of the Mugen package doesn't bother me, but the amount of battery charge doesn't seem that fantastic. Longer than the Nokia battery, but not that much longer.