Well I got somewhat chastised for commenting on this issue previously, but as the debate rages on unabated I continue to see posts where people are clustering into 2 groups.
This is not uncommon, like many recognized Nikon issues people generally tend to split into 2 camps.
Camp A: Worst problem ever camp. Camp B: Nothing to see here camp.
People in Camp A got a bad camera and are angry because they spent $2000.00 and Nikon wants them to pay to ship their brand new camera for maintenance. Also they have shutter withdrawal because they feel they can't shoot their new camera. People in Camp B got better or good cameras and get upset because they feel the Camp A people are somehow diminishing their purchase or being hyperbolic (and indeed there is some of that - but it also carries to brushing off reasonable complaints). At least this is my impression.
Usually the truth is somewhere in the middle. That is almost certainly the case here. Admittedly this debate is clouded by the complaints of 'dust', I myself used that term to cover the 'spots' issue. However, we are not talking about dust here, at least the vast majority are not. Dust would not be visible in photos at wider apertures, yet people have spots in photos as little as f/5.6. This is debris and oil and it is unacceptable to everyone who has the problem and not an issue to those that don't. I may add that like Thom Hogan I actually see this issue as having a higher incidence level than your normal manufacturer defect. That may still make it uncommon, but it was common enough for me to get 2 of them back to back.
It is not helpful to suggest that almost every d600 has this problem and people are in some conspiracy to cover it up. Accept people got good copies and you didn't. Maybe ask where they bought so you can tap that supply.
It is also unhelpful to suggest people are being silly when they complain about the fact that their camera has this issue and suggest that they are creating it using unrealistic shooting. This problem is too well documented for this to be a reasonable response. Accept they got a bad copy and be glad you didn't. I would add that consumer complaints are the only way we have to get companies to improve. After all the muck Nikon got in with the d600 and d800 issues they released the d7100 which appears to be problem free - that is a good sign. We should be encouraging people to report problems, not trying to discredit them.
I returned 2 D600s with this issue, to me it is unacceptable. If someone else wants to clean and re-clean lubricant off a sensor than I don't say that is unreasonable - it's their choice. So is returning the camera. Both are options, if you have a bad copy.
People who got good copies are indeed fortunate to be shooting one of the world's top 5 FX DSLRs.