DO NOT BUY OFF-BRAND BATTERIES!
Customer Rating: 




I had a DigiPower battery, which is made in the same factory as some other off-brands. The new features by the "e" version of the EN-EL3 battery did not work with this battery, meaning I had no idea how much charge was left.
In my D80, the off-brand battery would occasionally not work at all. If it did, it would report a full charge regardless of the actual charge. In my D90, the battery reports a fully dead battery regardless of the actual charge. Because of this, the camera does not function- it won't take pictures if it detects a dead battery.
In short, off brand batteries do not work at all with the D90. They work most of the time, but without the battery indicator, on earlier cameras.
The Nikon battery has none of these problems. As others have said, its battery indicator is actually VERY accurate.