>>Did they pay for the shipping? >> >>Jason > Nope...I paid for shipping the camera to Nikon.
I asked somewhat rhetorically, although there have been isolated cases of local Nikon repair depots covering shipping, the official policy is that the customer pays. It is nice that they turned it around quick for you - but I would be arguing with any company that wanted me to pay for shipping so they could fix a known defect in their product. I wouldn't call that positive customer service, especially if my camera was only a few months old.
In any event, it is very good that your d600 is back in action, it is one of the best DSLR's in the world and Nikon would be better served in my opinion to be more transparent and proactive about these issues in the future - and to not ask customers to spend money so they can fix manufacturer defects. As it is they have made it so most people HAVE to ship by refusing to provide parts to 3rd party shops.