Actually, I shoot high apertures from time to time. Nighttime shots on a tripod at f/11, and fireworks. I bought the D600 for our trip to Disney back in October last year. It had only been available a couple months (so I have one of the first few batches). And, before the "dust storm" issues started circulating. I had been going through photos at home, but it wasn't until I started hearing about it on the internet, that I notice my dust problems.
Again, my issues were minor. 95% of my photos were completely fine. Where the issues came up were when I used high apertures. Even then, you wouldn't notice them unless you were actively looking for them. That's in part because most of my high aperture were nighttime shots. Feel free to browse my October 2012 trip report. Hey, maybe we'll start a game, "find the dust!".
http://www.disboards.com/showthread.php?t=3010979
Now for the white wall (that mimics no real world shooting scenarios whatsoever):
I have never sent my camera out for professional cleaning. Just a few blasts of air. I never physically touched the sensor.
This is from my D600
today. Exif info is intact, so you know it's from me. This is at f/22.
Straight out of the camera
Lightroom enhanced from RAW. Highlights +100, shadows -100, blacks -90, WB. (Again, settings you would never use in the real world)
And for the nosey pixel peepers. My actual Raw file. Caution, 25MB.
https://copy.com/nLwFERNnalOX
Yes, you will see dust spots if you look hard enough. I haven't cleaned it in a while. However, what you are seeing here is as clean as any sensor in use right now.
I challenge anyone to post a cleaner sensor from their camera (any manufacturer). I think I have about 15,000 clicks on my camera. Or was that 25,000. I can't remember how many times the counter rolled over.
If I were looking to get another camera, I would wait a couple weeks to see how far prices will drop on the D600 and pick one up. Some websites have said later D600s had fewer dust/oil issues. No real way to confirm that, though.