I am still a bit shocked that the camera has lower MP, but if the high ISO is anywhere close to the hype, it would be worth it.
I am concerned that it is said to no longer autofocus with a f/8 combination of lens and teleconverter. I could AF my f/4 lenses nicely with a 2X TC and my 1D MK III.
This is a big take away for birders or others who need longer telephoto lenses, and even 800mm is not long enough in many cases, the 800mm f/5.6 will no longer AF with a 1.4X TC and the new body.