So just thought I'd share some findings that happily surprised me today. I have a wedding this Sunday and decided to to rent the Tamron 24-70. As always I setup Focal to calibrate AFMA all the rented lenses. I was surprised when it came time for the Tamron that it's focus accuracy was right around what I get with Canon's L zooms. The only other Tamron lens I've owned is the Tamron 17-50 which while a great lens has fairly large focus accuracy issues. For this reason I often use it at f/4. It also sharpens up nicely I've noticed vs 2.8. Anyways, attached are the Focal reports for both lenses on my 50D and the 24-70 on my 5D. We'll see how well it does Sunday but this definitely gives me a little more assurance than before.