I've re-joined after some time in order to offer my two cents worth.
I had a D800E, which I simply did not like. Mainly the shutter and mirror action. It took great images, but that's not everything. I've had many cameras over several decades and one gets a feel for the mechanical devices in one's hands. For example, I loved a Nikon S3 many years ago, and three manual focus Nikon SLRs. I even liked the Olympus E1 despite glaring limitations. I like my D810 a lot. Don't love it, but really like it.
So I'm saying, don't just read reviews, I suggest trying cameras in your hand, and if you will in your heart.
I also have a D750 I bought a couple weeks ago (new - supporting our local camera store). I just wanted another body, one for general people use (24-70mm or the Tamron 45mm - nice lens) and one, mirror up, electronic shutter, delay, tripod etc. with ultra wide (the 17-35mm, still a great lens) - obviously, the D810.
True, the D750 is not "professional" like the D810 - no shutter over the eye piece, has scene modes. But it's easy to set it up pretty much like the D810, and when I don't feel the need for 36 MP it's lighter and easier to autofocus. Like the D810, I don't love it, but I like it a lot. No regrets.