One thing that I never knew about until I went poking around another board was the DK-17M magnifying eyepiece. I ordered it, removed the stock eyepiece on my D800 and replaced it with this and I really prefer it over the slim stock eyepiece. It's not a must but does provide better ergonomics and image view. Was not an option with the D7000 and I guess not going to be for the D600 either.
check out the D600 brochure on the main blog: