Chris, loads of us use third party grips, most reccomend the Meike brand but there are some who are reporting problems since the recent D800 firmware update, others say Vertax Pixel grips are better, some suggest Polaroid, and some say any cheap old thing will do, whatever your choice theyre far far better value that the OEM grip and do exactly the same job, some do a better job with added functionality like an LCD panel, if you choose the Meike ask the Vendor if its been tested on an updated firmware D800, google suggests Meike have already fixed the problem but there will be loads of older stock out there, my Meike is absolutly fine though and my D800 was running the latest firmware, also picked up a used Pixel one on the cheap and that occasionally "freezes" and needs unscrewing and re seating.