I have an early D600 that did have the spot problem. I'm comfortable with using a wet sensor cleaner. I used one once for the original oil spots, then again after a guide threw sand all over my camera in Antelope Canyon when he wanted to highlight a sunbeam. After that I had to totally clean my camera. I have taken about 1K exposures after that with no evidence of spots. Basically, I have found that the spotting problem is a lot of furor over something that's trivial to fix.