A couple thoughts. I started with the D70s, upgraded to a D700 last year and added a D7000 a month ago.
The D700 is an amazing camera. I have been super happy with it. It takes great pictures in a lot of challenging locations that I have to shoot. It handles ISO 3200 very well and even ISO 6400 is reasonable. Both can be "fixed" in post to look like they were shot at much lower ISO. The camera is heavy and built like a tank. It is also more expensive all the way around. The body costs more, the lenses for it cost more, the filters for those lenses cost more. That said, it is my go to camera for most things.
The D7000 is also an amazing camera. If I had gone from the D70s to the D7000 I would have been just as blown away by it's capabilities. I would consider ISO to be good up to 1600 with 3200 being reasonable. Those seem to me to be about the same as 3200/6400 on the D700, so at least a stop loss there. The body, while not built like a tank is built like a Humvee. It is smaller by a bit than the D700 and seems a lot lighter. It also works with DX lenses, which tend to be smaller, lighter and less expensive. As are the filters, etc.
The D7000 shoots video. While not that important to me I am finding uses for it. Ergonomics are nearly as nice as on the D700, but some missing buttons and switches are a bit annoying if you are used to the D700. Nothing major, but there.
Images are as sharp on either, not complaints there.