Derrel,
I never said there weren't great old lenses (I know there are), my question was how many people that drop $2700 on a new body equip that new body with 40 year old lenses? I'm sure there are a few, no doubt, especially connoisseurs like yourself. But I would guess they comprise a minority of new camera buyers.
Most novices just getting started today have little desire to scour the used lens bin at their local pawn shop looking for glass they have no idea even exists. I would hazard a guess that most new users, like myself, shop for newer lenses. Most new users will assume a new lens is better than a 40 year old lens - right or wrong.
Yes, the Canon mount is cool as you can use Nikon lenses, Canon lenses, M42 mount lenses, Leica R mount lenses, etc. But I'll probably never buy one of those old badass Nikon lenses or an adapter to use them. I simply have no desire or need. I've yet to meet anyone who did have any interest... and I know some diehard Canon shooters who have been shooting professionally for years.
As for image quality, as soon as I find something wrong with one of my images that I can attribute to my Canon L lenses being deficient, I may switch to Hasselblad or maybe even a D3x. So far I've been nothing short of amazed with the performance of my bodies and lenses. I can afford a D3x if I wanted one, but I honestly don't. That may change. I've done stranger things than dump all of my gear to switch to another brand.
