No, it wasn't luck. Some of the D600s have had production issues, but I bought a refurbished D600 that had 217 shutter actuations and no dust or lubricant on the sensor. It's still very clean after a couple of thousand more images.
The D600 is an awesome camera. Very nice image, by the way.
"Red is gray and yellow white, but we decide which is right ....and which is an illusion"
When I see spots in shots, I shoot a picture of either my computer screen set to an all white image, like a blank page in my word processor and shoot at f/16. Then I use the levels adjustment in PS6 to increase the contrast. It will show the most minute dust speck. So far I have only had to blow off a few very small items with no wet cleaning required.
The above shot was just to illustrate how the D600 performs in very low light at a fairly high ISO. The colors were great even with the mixed light of florescent, incandescent and Christmas tree colored lights.