check this out for a bit more detail.
Not all the people reporting issues are as poor at photography as your comments suggest.
Yep, lots of experts there...
Like the person who states, "I may also try on a T1i to see if FoCal can come up with an MFA number for my 50/1.4 on that." I wonder how much luck he'll have with that.
Or all the people saying the 70D has inconsistent AF…but they're using a 50/1.8 which is one of Canon's poorest-focusing lenses.
Or the person who states, "AFMA should generally correct across the range" of distances, which is far from true.
So, we have a few complaints on the internet, lots of poor testing by 'experts', and the known reality that in any production line there are defective units that make it past QC, so there are undoubtedly a very small number of actually defective units out there.
That, and claims of a Canon coverup. Egad, we'd better all switch to Nikon, where that sort of thing never happens.