My D3X and D3S are so neglected sitting in the cupboard. I have not found any days when it would be better to use them rather than the 800E. For field use the D3X always travelled with a tripod, the D3S needed longer lenses. So the 800E kit is much lighter. I can wear it on my waist. If this was not enough the much better DR and flexibility of the RAW files would clinch the issue. It has no problems with black and white cats, or white flowers on dull days. The D3X needed great care and in my hands multiple attempts and HDR for these subjects. In the field say with flying Oyster Catchers you only get one attempt. The 800E delivers black and white detail on a realistic sky.
36 good MP allows more DOF control by stepping back and cropping than is ever achievable by stopping down. Now my investment in the best glass pays off handsomely.