ONLY Agree with him when it come to everything shorter than 35mm.
For 35 and longer, they're good enough if you're not going to make huge print and smell the bokeh.
Currently I only own a CV12. You will have to use corner fix on it for corners.
I did use some CV lenses on M9. Just my personal feeling with them.
21/4, forget about this, it need a lot of correct (The whole left side look soft to me, may be my copy was not a good one?)
28/3.5 sharp enough and high contrast on M9, but easy to clip high light and shadow.
35/1.4 SC which is fine except for some distortion and purple fringing.
50/2 Heliar(250th) nice and sharp lens.
50/1.1 sharp enough for a fast lens. but purple fringing may be a problem.
Which is totally fine for me when it come to actual shooting. Never has a problem.
Comment on Ken? Meh, period.