You mentioned that your guess is that more than 80% of D600s have the dust issue then you mentioned that we shouldn't trust those proud people that claim they haven't seen dust. Couldn't they be of the remaining 20%?
I have the dust issue in mine and I understand the frustration. I wouldn't complain about the problem if I didn't shoot at f11+ a lot for long exposures. Now truth has to be said that the camera is phenomenal especially for the price, so I disagree in not recommending the camera. I have sent mine for cleaning for the first time and will post my update when I get back the camera.