D600 dust - fixed??

It absolutely does not affect all bodies, or even most of them I suspect. I have two without issues, one purchased on release day, one purchased in January. Several colleagues have dust/oil D600's as well.

My personal belief is that Nikon has not issued a service advisory because they have not seen a large enough percentage of "affected" cameras yet. Nikon has a long history of issuing service advisories, so they are not afraid to do it. That is just my opinion however, as that is how it works in most other industries. If the problem is with a few, they deal with it case-by-case. If the problem affects a large percentage, or if there is a safety issue, they do a voluntary service advisory.

Just buy one. Chances are it will be fine, and if not, take 60 seconds out of your day to clean the sensor. There seems to be a very select few who have a legitimate issue where they need to clean the sensor every couple hundred shots, the rest are whining because they can see a speck of dust when they take an F57 macro shot of white paper with the exposure pumped in Photoshop.

Also, ignore the tin-foil-hat wearing folk on here that absolutely insist "every D600 has an issue", even when every imaginable test proves otherwise.