>just got my D4 .. question - I thought that I read that the >D4 and D800 used the same battery ..
The D800 with the grip (and suitable accessories, I think a different door or some such) can use the same battery, but does not inside the camera.
If you use a grip I am told there need be no battery in the camera itself, and you can just put a D4 batter in the grip, then both have the same. I haven't got a grip so I have not done that. yet. It's intriguing then you just have one (dual) charger, and can travel with only that one (large) charger instead of two.