I've been using the D3 for some time now after previously having a pair of D700s. I was always led to believe that the D3 was just a bigger version of its smaller brother but I've found its a great deal more than that. There are a few things I prefer about the D700, largely in terms of the handling and functions, but on balance, the user experience is just so much better. Somehow, the D3 is so much more responsive and in the words of Ken Rockwell, "never gets in the way of the pictures." Yes, once you've used a real pro body, its difficult to go back. Sure, it lacks a built in flash which would be useful as an off-camera slave controller, but I'm not a big fan of pointing a flash directly at a subject even if if its not adding any illumination. Its also a bit of a bugger to carry to say the least but these days I tend to lug around a D3100 on the bike, etc, which is a real joy. As long as its got a descent lens on the front, the image quality is just about the same in good light. So the D700 has become a bit redundant apart from as a back-up. The auto-focus system is supposed to be identical, but somehow its a bit snappier. Low contrast or dark subjects are still a challenge, such as the first dance at weddings, but I find this is also very dependent on the lens choice. Probably the biggest plus for me though is the double card slots. Many more "pro-sumer" cameras are coming with this feature these days and its very good news. Knowing that you have an instant back-up in high pressure situations is great for me and the client and takes away just on of the worries on a shoot. I've only ever had one card corrupt (and I managed to retrieve it) but that dread is always there. Anything that removes uncertainty and allows you to concentrate on getting the best photos is invaluable. Perhaps its just a case of "new toys" but I'm convinced that the cameras were not created equal and I'm certain (although I have no empirical evidence for this - just a hunch) that the D3 has a better dynamic range. My D700 has done me stirling service over the last 3 1/2 years so I can't complain. Its gone way beyond the rated shutter life and is still going strong - I'd buy another one as a back-up if they were available as it has done everything I've ever asked of it and 12mp - with the right lenses - are all most people will ever need. But I'm very happy I upgraded.