is this battery grip worth the money??
That's a tough question, since value is a subjective quality. I will have to say it is worth it to me. Very solidly built and integrates with the camera perfectly. Battery life is already excellent, so I can't wait to see how many weeks of shooting I'll get before needing a charge. It does add considerable weight to a light camera - making it even heavier than a 1D model - with two batteries loaded. Does balance the camera nicely with heavy L lenses and obviously makes shooting verticals fluid. I opted not to get the off-brand (not even sure its available yet). You see a lot of them for sale used (for the MkII, etc), and I assume that is for a reason. The electric components are the heart of a digital camera, and its not worth the risk of killing the camera to save $150. It is less than the grip for a D800 if that's any consolation. For me its worth it.