Ade-oh
Well-known
Interesting, this. OM lenses must have VERY variable QC. The ones I've tried (not many, and long ago), and the ones my friends have tried (that I've seen real pics from, not web) and the ones I've heard of manufacturers testing (unfortunately I'm not at liberty to say who did the testing), have all done quite badly. And yet there is a ferocious fan base on the web.
Etc, etc...
My opinion is based on using the OM system for the last 32 years, alongside Nikon and Leica. I'm sure there are differences in resolving power and so on if you dig down into shooting test charts in lab conditions but as you know very well, Roger, under normal, practical shooting conditions and stopped down from open aperture, a lens would need to be really, really crappy to show much difference in 'sharpness' from Leica or Nikon. This is not meant to be offensive but your opinion - with the added thrill of secret lens testing! - sounds like the testosterone-charged brand snobbery which was rampant in consumer photographic magazines in the 1970's, alongside the topless girls.
As I say, I use Leica, Nikon and Olympus cameras in 35mm and I honestly couldn't tell the lenses apart for 'sharpness'. Distortion, particularly with wide-angles, is another matter but probably reflects the fact that the Zuiko designs are getting a bit long in the tooth now. I doubt they are all that much worse than Nikkor or Leica lenses from the same era.
So why is there such a fanbase for OM cameras and lenses? Because they're small and light, they work, they're reliable - I've never had a problem with any of mine - and, by and large, they're remarkably cheap for what you get nowadays in the secondhand market. Are they better than Nikon, Leica, Pentax, Minolta, Contax etc etc etc? Not in any measurable way, but neither are they any worse: in the hands of a competent user, they will produce excellent results.