Now how do you check the IQ? Just eyeballing is good enough or there is more involved and accuratemethod in here?
Paul, Thanks for your input and my lens has "3" in the third digit in the serial number. According to Canon this is a new version lens and should be problem free..
Glad to be of help / some input.
About "checking the IQ"... if you do some "home made tests" (try both on tripod (IS off) as well as handheld) focussing on a brick wall, some text / books (from a distance) in both landscape and then portrait that should help you see. Apparently it is usually quite obvious if you do a few of these tests to see the difference comparing landscape to portrait orientation.
But as your lens has "3" in the third digit, it seems like you should be ok. I'm glad for you. Are you happy with the lens?