Interesting thread guys. I am ambivalent about getting a Nikon grip, but price locally is $299 so isn't too bad. Otherwise $100 for the Pixel sounds interesting. I might check out what my local dealer has in the way of third-party grips too, I have never inquired. If I do get grip, likely it will never be on tripod or monopod.
BTW I have the Markins bi-directional plate on my camera and it is the nicest one I have ever owned, beautifully rounded shape contoured to exactly match the D800 contours. I normally mount my cameras in forward orientation on my gimbal or else on my tilt-swivel that is mounted onto my monopod.
D800 isn't my only camera, and most uses I have for it don't involve portrait format. But yes am guilty of that overhand portrait grip, which is really bad technique, although being a left-eyed shooter isn't as bad because my right elbow can be held against my body somewhat.
So I'm down to the $199 difference which might be close enough to tip me over to the genuine Nikon one. Had Nikon offered more fps in FX mode, like they did on the D300 and D700 with grip I would have been all over it. I do use the very handy 5fps mode available without grip in 1.2 crop (30 x 20 format).