If you had a Mk 3 within the affected serial no. range BUT think the AF has nothing wrong with it would you send it in to Canon anyway?
I got mine a month ago and to me the AF seems great. I shot some of my boys rugby today and out of about 250 photos maybe 10 were OOF.
I shot mainly with Continuous AF track priority but also tried Main Focus Point Priority.
Tracking Sensitivity on 0
Enable surrounding assist
AF Priority/Tracking Priority
And also with PIX's Picture Style.
Here's one of my son making a tackle - SOOC. I know it may not be perfect to blow up to 30x20 but what do you guys think.
F4, ISO 640, 1/800
Its a tough call. Depends on whether you are concerned about resale value down the road. If you are, what do you think will be the first question most folks will ask even if it looks brand new, shoots perfectly, and washes your car for you?