There is no doubting the D800 models are going to be popular purchases, that is already very apparent.
My thoughts are again though focused with my experience having shot extensively with the D3x and various medium format options.
The user will need to be at the top of their game in every way. Otherwise they will not reach anywhere near the cameras potential on a regular basis, and could end up with lesser results or certainly no better, than with a lower resolution camera.
In more specific personal terms, I am not overly struck with the grip, too small were my first thoughts, and not enough room between it and the lens mount. I would not say it was uncomfortable, similar to the D7000’s grip so not the most
comfortable for me.
Those with large hands may or may not agree, those with smaller hands will find it quite nice I suspect.
No adjustable viewing angle of the rear LCD display is my other disappointment, but otherwise I like the way it handles in other ways. For example the menus feature some sensible changes.
This is pretty much a D4 in many aspects of specification, and in that sense for its cost, a bit of a bargain. But just be sure you really do need those extra pixels.
Most I suspect will probably not. The resulting workflow changes that may be needed, not just in technique, but computing performance, post capture time and storage, could herald quite a change to existing approaches if the benefits are to be seen. However, let me say that when it does all come together…wow. So if you are awaiting your camera, there is time to spend mulling over some of these other aspects.