I have the Tokina version which has the same optics. The Tokina is supposed to have better coatings, although they don't look quite as good as AI Nikkors - the reflections are brighter. The build quality is also supposed to be less solid than the Vivitar, although it still appears to be a very well made lens - in the hand feels as good as any AI Nikkor.
I haven't used mine much, mainly because I have too many other macro lenses to choose from
From my limited experience, it is a sharp lens. Wide open there is some loss of contrast and an overall softness to the image although it is plenty sharp. Contrast increases on stopping down a bit. Given it's reputation for good bokeh I was a bit disappointed with the background rendition at medium-far distances - it's not bad but I think the 105/2.5 is better. At closer distances the bokeh is very nice
Mine came with the 1:1 extender but I sold it as I bought it mainly to use as a medium-tele/portrait lens that can focus closer than normal (why do all 85mm lenses only go down to 0.8-0.85m?). I have other options for getting to 1:1 which gives me more working distance.