Just received my D810 today but haven't had much of a chance to put it through it's paces as far as AF speed and accuracy etc is concerned - these are the main attributes I was looking for as an update. I am hoping to get out tomorrow and really put it through it's paces. However, a few things I am very impressed with are the shutter quietness and vibration, it is amazingly quiet and almost no vibration. I liken it to my friend's Canon 5D MKIII which I have always commented to him is very very quiet and have to apologise for scaring away birds when we are shooting together with the clunk, clunk, clunk of my previous D800E. I am exaggerating a little, I don't think I have actually scared birds off, some birds would look at me when I let the shutter fly but never actually fly away, maybe that's a good way to get eye contact? Anyway, there was a marked difference between the D800E and the Canon 5D MKIII as far as shutter noise (and probably vibration as well), but now that is a thing of the past, the D810 is very, very quiet and almost no vibration. Very impressed!
The new VF seems a tad brighter, and the display writing in the VF is white rather than yellow if that is an issue for you - it doesn't bother me.
The grip is a tad deeper, but not all that much different, probably better for big hands, but mine are not big, just average I guess and I don't find it better or worse than the D800/E. The rubber inserts have a slightly different pattern that gives a slightly more positive feel, again neither here nor there as far as differences are concerned with the D800/E.
One thing that is omitted is a flash hotshoe cover. Not a big deal I know, but really, has penny pinching come to this? If you don't want one, then take it off, but I do like to have one and I had to steal it off my old D800E.
As I said, I hope to put it through it's paces tomorrow and have a better report as to how the AF fares as far as speed and accuracy is concerned. As it stands, the quietness and lack of vibration is a really big plus, very, very happy on that front.