My center point focus is very erratic on my faster lenses (35mm F2 (non-IS), 24mm STM and 17-50 2.8) when focusing anywhere from 15, 25, 50+ feet. When it misses (quite often) it tends to front focus by varying degrees, which makes AFMA useless. If I switch one AF point to the left or right of center, the problem goes away.
This 70D was bought brand new from Adorama in November.
If I had the foresight I would have returned it in within the first 30 days, but there are so many posts out there blaming AF issues on the users, so I figured I had to to my homework and learn about the "more advanced AF system" and how to properly do tests (I am not passing the blame, I get why this is an issue for many cameras, but I think the 70D issue is a special case). I should have went with my gut in knowing something was off about my new body. There was just a lot more to learn coming from a 450D, even assuming I had a 100% functional new 70D body.
I borrowed my Dad's T3i for spurts of time to make sure my lenses weren't out of whack or my technique. But his center point functions as expected with the faster lenses.
With the 19AF points, it does make it easier than the 9 point AF system to use non-center points, but it's kind of a bummer that my camera's most accurate AF point is the least reliable for shots. It also makes using the center zone mostly useless as well.
I'm going to Hawaii in a few weeks and plan to use my off-center points for the trip. After then I'll try and deal with my Canon warranty. I'm assuming I will get the "electrical calibration/adjustments" the first trip anyway.
This experience has kind of bummed me out on my Canon gear. I was super excited to jump from my 450D.