Thanks Richard. I shoot wildlife with the D700 at ISO 800 all the time and have no noise problem. I've not personally used a D7000, so your characterization is very helpful.
If we assume, for a moment, that the D800's noise characteristics are similar to the D7000, albeit with more MP's, then I'll likely be sticking with the D4 at this time, then when one of my D700's gives out, move it up to a D800, perhaps at the end of the year, rather than fix its shutter which will be nearing, or have exceeded its useful life by then. Under that circumstance I could justify it, and we'll know much more about the camera by then.