To OP: There are 2 versions of the M-ROKKOR 90: the CL and CLE versions. The CL version has the shorter/steeper RF coupling cam designed for the Minolta/Leica CL. In Minolta's later CLE camera and lenses, Minolta used the standard Leica M cam length/slope. There are comments on the web saying the CL version lenses can produce focusing errors on non-CL bodies and that the CLE versions are the better choice for full compatibility. I haven't tried a CL lens on my M bodies.
I have owned 2 CLE version M-ROKKOR 90s and both were great performers. The first copy I owned was a bit rough, but performed well. The second copy I owned was very clean and was sharper than my previous copy. In my opinion, the M-ROKKOR 90 is practically flawless, and a no brainer if you want an inexpensive 90 in your bag. It has noticable falloff until about f8, but has great sharpness and nice OOF areas from f4. I'm sure there are countless exmaples of it's performnace on Flickr, if you take the time to search. Below is a shot from the 2nd copy I owned. I let my M-ROKKOR 90 go when I bought my MEM.
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