I bought the lens new from an online retailer. As soon as it came in, fired some test shots at f/2.8 and f/4 - the images had nice colors but were soft. At f/4 were on par or softer than my 24-105. Ran the batteries test - the lens was backfocusing about half to two thirds of an inch. Took the lens to a party and used it with flash at f/6.7 and got some nice shots, but not great.
Pondered for about five minutes whether to play the dealer roulette or send it in for calibration. The very next day I sent it in to Canon (New Jersey) and in a day they calibrated it and sent it back overnight. Now, that is a lens to have. Outstanding sharpness and macro ability. Wow!
It simply boggles the mind that Canon would ship out the lenses so mis-calibrated, unless it is a secret plan to show us how good its repair centers and customer service really is.
The problem is that now I need to improve my technique, as I won't be using the IS crutch anymore.