But after using it a while and comparing photos taken with it, to my L series 24-105, I was routinely disappointed with the sharpness I was getting. I took a lot of outdoors, nature photos with it, often of birds and flowers/landscapes. Most of them were OK, but none of them really popped the way my other lens(es) did.
Most likely this is the result of the camera needing an AFMA update for that lens (auto-focus micro adjust).
The problem for zoom lenses is that it can often need two different numbers for wide and telephoto, a feature that is only present on newer Canon DSLRs.
This is not a problem that is specific to Tamron lenses.
However I will say that it is not possible to have this particular Tamron lens calibrated in the same way that Canon lenses can be.