Do you get a special quality using this lens that is not possible with one of the Micro Nikkor 105/2.8 lenses? …..think there are at least 3 different versions (AIS, AFD, AFS).
If you have one of them it could be interesting to see how they differs? bokeh quality, sharpness etc...
Maybe it is not possible to focus that close with one of the Micro's…..or maybe quality declines a lot if you use extender or bellows…..