Really, really happy with it. I think I might have to go with a back-up D7000 or something for motorsport (lots of very narrow aperture shooting) next year as presumably dust will become an issue, but the D600 is a keeper for everything else for sure. Love the handling and it's just effortless, Auto ISO set to 6400, never need to worry about quality degrading.
I have the 28mm 1.8 at the moment but not sure on the focal length yet, I think a 50mm 1.4 will cover all of my needs far better. Off to NYC with it on Thursday, can't wait!