Here's what I think about the 24-70 I's quality control issue, softness, copy to copy variants or whatever it is. The 24-70 f/2.8L is very popular, every Canon shooter I know has it and for most of them it is their first L lens for their xxxD and xxD bodies. Most of these newbies, myself included, thought that If we spent $1100+ on an L lens then it should produce the sharpest images that they had never seen from their 18-55 or 17-85 kit lenses. They became disappointed to find out that their $1100+ L zoom is not much sharper than their kit lens. I think 95% of the problem of the 24-70 started from this group.