Got my D600 back from Nikon went out for my first photo shoot and already over 50 spots! I can't help it I'm mad. I think Nikon should have recalled the D600's with issues and replaced them with the D610…the camera they revised to alleviate their mistakes. i'm surprised no one has started a class action lawsuit.
Keoki, I had the same problem and sent mine in 3 times before getting a refund. Please stay on top of this. If you don't yet have a supervisor on your case, request one. You might need to send it in 3 times before they will consider a refund.
I had the spots show up on the very first test photos after getting mine repaired all 3 times. Prior to sending mine in the first time, I tried in vain to clean the sensor myself; however, the problem was that I couldn't remove many of the spots. It's just my opinion, but what I surmise to be at least part of the problem is that Nikon can't remove all of them either so when people get their cameras back, they still have spots. Whatever the stuff is, it is REALLY sticky, or possibly it stains the sensor (again, just my opinion).
Here's the thread chronicling my service repairs for the D600. Please know you are not alone. Vector and I were fortunate to be granted refunds. Be firm but polite so they take you seriously. If you get bent out of shape, I don't know that they will work with you. As frustrating as the process is, please know at least a couple of us have walked in your shoes and know it's a royal pain-in-the-arse process to go through.