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what do you do that makes you feel the need for those bodies you mentioned?
I've recently gotten into hiking so mainly I want something that can handle the elements better; get wet, dirty, and banged around. Think war zone photography on a less rugged but similar scale. The D700 did quite well, through rain, mud, and clouded mountain tops, but just doesn't feel like its solid.
The "feel" of the camera is one thing - actual performance, at least my own record, seems to indicate that a lightweight prosumer body will do just fine. I've done pretty nasty stuff with my D90 and D7000, and they never failed. Never even showed the marks of having been out in dust and rain for weeks.
If I were to carry something heavy into the backcountry, I would maybe consider a D800e for it's sensor, but not a D3. The weight difference over my D600 body means I can carry more lenses, or a panorama head, a stronger tripod, or other stuff that adds real capability, all at the risk of possibly having the camera fail. However, so far that has never happened, nor is camera failure a life threatening event. Out in the backcountry, the camera is not the most important gear item.
I'm by no means one of these "ultralight" hikers who push their "base weight" lower and lower, but every ounce counts, either allowing more food or more camera gear to go into the pack while staying within the threshold you know you can handle easily. Everything becomes a compromise when putting together gear that has to be carried into the backcountry.
Obviously, much of this only matters in overnight hiking situations, but that's what I do, and for those trips the weight of the camera is more relevant than its rugged construction. Zip lock bags and gaffer tape are great stuff, and nearly free. Tape up the camera and bring an extra lens.