>I have a couple of questions. Do you have to have an ENL3 in >the camera for it to work with the MB10? Does the MB-10 stick >in to the existing battery slot like the D100's battery pack >does?
No and no. The MB-D10 fits the D300 (or D700) without having to remove the in-camera battery. On the other hand, the combination still works with a single battery in the grip, or with a single battery in the camera.