I use a D600 with a D7000 as backup. When I got my D600 I sold off or traded my DX lenses for FX, since I can use them on both bodies and as has already been mentioned, the DX sensor sees the center of an FX lens so get the optimal focus area and less vignetting. Sometimes I miss a few of the lighter, smaller DX lenses, but only because they are just that, smaller and lighter. I am considering selling the D7000 now and getting a D7100 because I am very interested in the AF coverage area being so big and and having 51 points (it's frustratingly small in the 39 point system on the D600) and the 24MP sensor with no AA filter. These features may make for great wildlife and action shooting and the sharpest ever DX images. I am very happy with the D600, have been happy with the D7000 too, but more is more!