D600 dust/oil. Everybody is running around with their hair on fire. Is there really an issue?

Certainly not in number significant enough for Nikon to consider it an internal problem, and it's certainly not Nikon specific.

Yes, some cameras spray a little oil, but this happens to all brands, and cleaning the sensor takes less than 1 minute and is part of camera ownership.

5DM3 oil

http://forums.dpreview.com/forums/post/50059170

5DM3 oil

http://forums.dpreview.com/forums/post/50153872

1DX Dust/oil to the point of being unusable after only a few months:

http://www.fredmiranda.com/forum/topic/1153198/0

Canon's own service advisory for 1DM3 and 1DSM3 due to dust/oil:

http://cpn.canon-europe.com/content/news/EOS_oil_spots.do

Those took me less than 2 minutes to find. Honeslty, your chances of getting a perfect D600 far outweigh anything else. Just return if if there are issues you deem unacceptable. Just don't use these forums as your primary source of information - as with anything, people are far more likely to post when they're upset than happy and it's not an accurate representation.

Also keep in mind people who say they never had dust before probably weren't shooting white walls at F22 and applying an exposure curve like it seems to be popular to do now.  It's no different than those taking 30 min exposures at ISO 12,800 of the inside of their lens cap and whining about a hot pixel.

I have 2 more D600's in my family now, and neither have an issue with dust/oil after plenty of actuations.

Best of luck!