I too recommend just spending the money on the nikon version. I have had 2 other aftermarket grips for other bodies, one caused the camera to act funny function wise, and the other, the cheap plastic wheel you used to attach the grip to the body broke, and made it nearly impossible to get it off my camera. I litterally had to take it apart and break pieces to remove it.
There are a LOT of people here who use the aftermarkets and claim success. They will all preach that, well, you can buy 4 or 5 for the price of the nikon, so just buy a new one when it breaks and you will still be ahead. Why even go through that? what if your shooting a friends wedding or something of importance, and that thing fails or screws with your camera electrically? Is it worth the risk? For me it wasnt, and honestly, after getting my first nikon grip, it was lightyears away from the aftermark in quality and function. worth every penny in my opinion.