This is a very interesting thread topic.
I am in the process of determining 'which' of the multitude of 55mm Micro-Nikkors to use to replace my 50mm f/2 AI-S.
I have heard the horror stories of the 55 f/2.8 Micro having oily blades, but
Coin Imaging rates it as the best of the bunch. (According to them,
the 3.5 AI is just okay and has stronger color fringing).
I may wind up getting the newer f/2.8 for macro, and (
as Bjørn suggested), "
Nikon tend to carry out tweaking and polishing the design of their lenses throughout the product life. Usually without making the alterations public. Changes could be modification of coatings or sometimes using a different kind of glass, or adjusting the thickness and spacing of the elements." I believe this to be true as well, and I don't think the f/2.8 versions have an oil problem any longer.
Trouble is, I am starting to fall in love with the older, non-AI, Nikkor lenses ... the ones with the scalloped, all-metal rings

This leaves me with a choice of the compensating aperture, pre-Ai, or the non-compensating aperture, pre-Ai. Namely, the topic of this thread.
I have always read the compensating "C" version of the Micro-Nikkor 55 f/3.5 was the better version ... until I read
this article from Thomas Pindelski. He says,
- "The modern DSLR user most definitely does not want the compensating version as the DSLR’s through-the-lens metering automatically detects the light fall off at close distances, so the duplicate correction resulting from the compensating aperture mechanism will result in over exposure at close distance."
Would like to hear some thoughts about this. Macro will be my primary use, less than 3'. Rather than get an extender, I will simply reverse for 1:1.