I recently sold my D200 and replaced it with a D600. My D300s will now become my backup camera. However the D300s will still be my primary camera for sports, wildlife, birds and aviation (anywhere where speed and reach is important).
I am still getting to know the D600, and so far I love it. If weight is not important I will always go with the D600, with 24-85 and 70-300 (or 80-200) lenses. However if I can only take one body and one lens (say, hiking in the mountains), the D300s with 18-200 wins.