I used the grip on mine for a short while, but in my opinion it is mounted too far forward (just a personal thing)...
The only valid complaint I have with the supplied grip, is that it does not lock solid when folded down. There is about a 1/4" of play in mine, which makes it feel like a cheap plastic knockoff... (Check Midwayusa if you're looking for a rock-solid forward grip)
I did however keep the pic-rail attached, which to me is worth the money in and of itself.
Tac-pac rail, GG&G adapter, Harris 6-9.