I'm curious why are you considering selling it?
Personally, I don't see a difference in 99% of my shots between it and my D600. I just picked up a second, gripped D600 for dirt cheap (now getting serviced - who knows, it could become a 610?), and a D7100 for my wildlife images. The D800 was supposed to play the role of 2nd camera and wildlife camera, but the files are so dang big, and at a max of 4 fps it just doesn't shoot fast enough when I want to grab birds in flight. The D7100's buffer barfs after 1 second (a problem), but I can work with that. The
huge files I'm getting from the 800 get cropped in LR, but the original NEF is still 36MP's, and shooting in DX mode tends to be an issue when I'm trying to frame a flying bird and keep it on the smaller areas so I don't often use DX mode unless the subject is stationary.
It's a great camera, but I just prefer using the D600/610. And if it's not getting used I'm thinking I should move it for something I can use, like a 70-200mm f/2.8 VRII.