I think it is pretty simple, what makes a pro body it's the guy or gal pushing the shutter release. Second it's the glass you put on the body. Third it is the camera it's self. Will it stand up the the rigors that you will put it through. Here the question has to be ask what type photography are you doing. Is it studio, sports, wild life or etc. Each is going to have it's own specific needs. I have a Nikon D2H that stands up under the pressure of a demanding sporting event with fast focus, 8 fps and and sealed well for all weather conditions. But when I move to micro or slower moving subject my choice is the D70 with it's higher pixel rate and lighter weight. When I got my first pro body I was thrilled to death. In 1971 the Nikon F was the gold standard for SLR's. At that time there were a lot of SLR's on the market that were just not made with the integrity that the Nikon F was. Most of those manufactures or not around in today's market. Those that are still here such as Cannon, Nikon, Pentax and Olympus proved that their equipment could stand the test of time. I am proud of the fact that the same Nikon F I bought in 1971 still can perform at the level it did 36 years ago. Will todays cameras in this disposable world be able to say the same? Only time will tell if they are a pro body or not.