A friend of mine who recently purchased the 200L 2.0 wanted to see how his lens compares against mine. We downloaded the Imatest's trial version and ran a series of tests. When we saw the results, we were so shocked that we ended up doing the tests over and over and over again under various conditions (multiple flashes, single flash, no flash, different shutter speeds, mirror lockups, different picture styles, and so on). The result was the same in every single one of them. My copy of 200L 2.0 was about 10-15% sharper (10% in center and 15% around the corners) than his. This is based on purely the numbers provided by Imatest (Cy/Pxl, LW/mm, LW/Ph, etc). There is also a visible difference between two pictures shot by two lenses if you look at them at 100% crop. How is this possible? This is a $6,000, how can there be such noticeable difference. The center performance is one thing (I still think 10% is a lot), but corners are different as much as 17% in one area. How the heck is canon producing these lenses and checking them properly in QC?
It wasn't just MTF numbers that were very different. The CA and SQF numbers are also very far off. My lens fares extremely well when it comes to CA (0.004%), his is twice and sometimes three times as worse. SQF numbers are no different, there is a 5-6 units of difference.
My friend got his copy from a retailer I am not going to name here (not Amazon). He is seriously considering returning his lens.