Interesting discussion! I think with the D700 Nikon reached a point where upgrading was no longer a matter of ultimate IQ issues for most users. DSLRs reached a new peak, so to speak. Personally, I love my D700, and have no plans on "upgrading" to any other Nikon in a long time. The reasons are quite simple:
1. I don't do video, as I haven't figured out a way to hang them on the wall quite yet.
2. The D700 produces all the IQ I want and need, as the prints I can produce at the sizes I want look spectacular, and continue to "wow" me.
3. I see no weight advantages. This one is big, as many people are arguing the weight savings of the D600 as a significant advantage. What I think they forget is that a D600 with a 70-200 is not that much lighter than a D700 with the same lens (or 14-24, or any other zoom lens for that matter). Both combos will give you scoliosis after half a day hanging on your shoulder.
4. I can use my D700 as a sledge hammer for self defense.
To sum up: To switch to a D600 from my D700 would cost me about $1000. In return I'd gain image quality improvements I don't feel I need, video features I won't use, no real weight advantage, and I'd sacrifice a ton of features I do need, as previously discussed in this thread.
What I WILL spend that money on, however, is the new Fuji X-E1, which actually DOES give me significant weight savings when I want a small camera, with no big trade off in image quality. Personally, I think this is a much wiser way to spend my limited funds, as I will have access to the best (fine, not the best any more, but good enough) of both worlds. Only question is... WHICH COLOUR!?