I got my third D600 today. Second photo was at f/16 of the blue sky, and it revealed one dust speck. I can live with that.
The back focusing I had with the two previous D600 bodies seems much better on this one. My 28mm lens back focuses only slightly, maybe not enough to even worry about adjusting the AF fine tuning, and my 50mm lens is perfect at 0 adjustment. I have not tried my 85mm lens yet.