I've been contemplating an FX format DSLR for some time, and finally made the move. Today I received my new-to-me D700. It's nearly immaculate in cosmetic condition and has a little over 3000 clicks on it. I figure it's got many more to go.
I will still be shooting my D300s, but I wanted an FX body for low light. The D700 is supposed to be good for this sort of thing, at least compared to DX format cameras. I shoot a bit of wildlife and a lot of animals come out at dusk. I have an F/2.8 Sigma 70-200 that I've been using on my D300s. I know I'll lose the crop factor, but I'm expecting the better ISO performance will help.
Anyway, the notion of using the same battery and grip (if I decide to get it) and the same control layout appealed, and a it seems a nice used D700 can be had very reasonably.