I didn't state the CO 60 is dull, just that it is clinical in the way it dissects a motif.
I did not find the CO 60 dull. Because I am a close-up photographer and because it had a large hot spot about 1:3 (if I remember), this was a serious problem for me. Also, IMO, it handled mottled light less well than other lenses, like the kind of light you would get in a forest, where sunlight was coming through in rays. For some reason, it seemed they blew out easier than other lenses, but that could just be me. Having done over 33,000 flat posters on a vacuum table (rock concert posters), the CO 60 would be a perfect lens for that kind of copy work. Worse, it had such a short focus throw that really fine work with it had to be done on a focus rail. Aside from its brilliant lens work, the rest of the design of that lens is poor, to bad. Not thought out carefully, in terms of focus thrown, hot spots, etc. -- especially if it was designed for forensic work.