Quote>Yesterday I pre-ordered my D800. > >I really can't remember where I saw it now but yesterday I saw >some really nice side by side comparisons at high ISO where >the D800 clearly 'looked' cleaner and better than the D700. > >The only question now, is do I sell the D700 with grip, like I >intended, or do I hang on to it for a while?<Quote<<
You may have to wait a while for the D800. If you do not have a backup camera, keep the D700.
If you list it now, ask a reasonable price (what the D700 is worth to you). The price of D700 bodies is going to go up and down like a YoYo because at some point there will be a perceived flood on the market. However, this is a niche camera. I think price & demand will rebound as there are plenty of photographers waiting to "move up" or get a second camera.