Canon20Duser: I have the S100. Any way I can tell if the lens is decentered?
I disagree. Even a photographer who does not see the defect in their shooting today may well find themself later taking shots where it does make a difference, or may advance in their ability to where it makes a difference. They deserve the lens they paid for. If somebody bought a lens with soft corners and didn't notice it because they shot only portraits, would you say they should be happy because they can't tell yet?