Lars,
I've shot with the D3 for the last 9 months, and absolutely love the camera. That said, sometimes it is just too darn big to lug along (for example, I didn't take it to the hospital when Rebecca was in labor with our daughter). I've often thought that I would be more likely to take the camera on "casual" photography shoots, long hikes, and social events if it were a bit smaller and lighter. If I had the decision to make today, I'm pretty sure I would go for the D700 over the D3.
The D700 is supposed to have exactly the same sensor and imaging pipeline as the D3, so the image quality should be the same. Although the faster frame rate, better battery life and dual card slots of the D3 are nice to have, they aren't critical for the type of photography I do, and I would gladly give them up for a lighter and more compact camera.
Keith
