Agreed, and I find many times a so so looking lens can result in very decent results. But where the tire meets the road, in those instances when you really need or want the sharpness, the lens ought to be able to deliver. I have quite a few that do, aand unfortunately, some that just do not.
I am still very happy with a Canon 35/2.0 I picked up cheaply from jiri_e and the sharpness is amazing; but after a shoot in the Hirshhorn the other day, with the lens wide open, I found that I got some unwelcome vignetting. I hope it's the UV filter that's still screwed on that I never removed. Otherwise I don't know what I'll do. (Sorry, it was a bit off topic, but addresses the issue that even a good lens, if a bad specimen, can result in an overall bad lens.)
And Raid, I now awake each morning excitedly going to RFF to see what today's avatar will look like!