Do I need the 24-70 2.8

Good Question. I am in the same situation. I have the d600 and only the 50mm and 85mm primes. I am probably going to a wide angle zoom next, but am not completely sold on the concept. I am starting to consider just getting the 24 -70 2.8 as well. I love my primes, but it's a real pain having to switch out lenses when shooting. I'm just a hobbyist like you but I like to have the highest quality.

Do you use your 28mm very much? Do you need the VR feature which the 24 - 70 doesn't have? I feel like I would, but I have seen so many mixed reviews of the 24 - 120 to be completely sold on it.