I've been reading all the various Nikon related forums over the last 3-4 weeks that I've owned my D600 and wanted to chime in on the current mess...
I've owned and used at least 12 different digital Nikon bodies over the last 10 years and I've become familiar with the necessity of dealing with sensor dust. However I've never had a single body that has the type of "dust" problem that my D600 has. While the shutter may have issues in some D600's that certainly could be contributing to the problem, thus far I'm inclined to agree that there is an issue with lubricant or liquid spots of some kind adhering to the sensor. Cleaning the sensor with various dry methods (blowing or using soft cleaning pads) removes some of the basic dust. However there are spots that won't come off without a wet cleaning and it often takes 2-3 tries to remove them using the wet cleaning methods. I took the D600 back to Calumet Photo where I purchased it and their tech who has been cleaning these digital bodies for years agreed that these spots require significant effort to remove - it even took him 2-3 tries.
So Nikon has an issue on their hands with the D600. I have an issue as well since I use it for video where the spots are a big issue that can't easily be corrected in post like a photograph. Basically I have a $2000 brick. I recently did some generic time lapse sessions to get the shutter over 5000 activations as some people are reporting that the spots decrease over time. I'm going to take it in to be cleaned one more time and see if things improve. Until we start hearing reports of a real fix from Nikon, I'm not inclined to send it in to them yet as they just said they would clean it free of charge when I called them on the phone.
That's without going into the HDMI cropped output issues. At least those can be fixed with a firmware change. *IF* there is lubricant of some kind coming off of the shutter mechanism, then my guess is that this won't be an easy fix for Nikon without pulling the camera apart, cleaning individual parts and/or replacing parts.
We'll see what happens...
- j
<edited for clarity>