I have the 2.8-4 D version and it is a good lens. This focus range is highly versatile. I used it on both D600 and D800, and even as my only lens for a month in Thailand. It is sharp enough and produced nice images. However, primes like the Sigma 35 f1.4 DG HSM, or the Nikon 50mm f1.8 G or Nikon 85mm 1.8 G do still add a bit more to the images.
I now use that Sigma as my walkaround lens, and while before that I thought I really needed a zoom, much to my surprise I'm seeing that I really don't miss the zoom at all.