It's the only thing really missing from my bag. I have an excellent copy of the Sigma 120-300/2.8, but it's bigger than I want to regularly schlep. And I don't want to schlep a 70-200 2.8 zoom. So my current decision is either a 180/2.8 prime or the 70-200/4 zoom. For the f4 zoom, the Nikon G lens is a no brainer -- and in fact that is the lens I was pretty well set set on buying. However I know that I will mostly use it at near 200, so a faster 180 prime enters the equation at about the same size/weight. The older Nikon prime is okay, but I've tried it and it leaves a little to be desired on a 36MP body.
What about the Sigma 180/2.8 macro? Anybody using it on an 800/E/810 that can share some insights?