I read those comments from people like Thom Hogan as well and they might be true, but he does mention that part of the problem is that faulty technique shows up more than it did in the past with the earlier digital cameras.
When I switched from the D7000 to the D600 I noticed much more sharpness with the lenses I use. Part of that is probably attributable to a better working combination of camera with lenses. I am amazed at the detail I get in some shots.
But you have to know your camera thoroughly and be aware of how the autofocus is handled.
The D7000 might have had slight focus issues, but as far as I can test the D600 is spot on with the lenses I have, especially the 70-200mm, the 18-35mm and the 85mm.
My files will be slightly smaller than those of the D800, but still big. The computer can handle it though, at least so far.
Post processing has been simplified somewhat because the files I get are already pretty good to start with. In most cases, at the end of PP, sharpening isn't even needed, I just apply a high pass filter.