Summary: I may have gotten a bad copy. It didn't autofocus accurately -- not even close. I had to return it. It does have a manual focus mode, which worked, but then it didn't function as a "walk-around" lens, which was why I got it.
Tamron 28-300mm f/3.5-6.3 XR Di VC LD Aspherical IF Macro AF review by glenwells
25 September 2013
Summary: I am a realist and read a lot about this lens prior to purchase. I have a 5DII and 6 lenses - 3 of which were expensive. It is all in a large now heavy camera bag. I stopped taking the 5DII out because of the weight and taking 2 or more lenses. I was taking a Sony NEX instead.
Tamron 28-300mm f/3.5-6.3 XR Di VC LD Aspherical IF Macro AF review by climbhigh4fun
29 May 2011
Summary: At the time I purchased this lens I was using a Canon 18-200mm IS. I Chose to buy this lens and give up the Canon for several reasons. One, I needed a little more reach, even though I gave up a little on the wide end, since I do mostly wildlife this wasn't a problem.
Pros: Compact and lightweight, excellent zoom range, SQF is great, VC outstanding.
Cons: Full frame it has some light fall off, but on APS-C not a problem.
Excerpt: I started by looking at the Tamron 70-300mm and then thought about the many times I've lost shots while switching lenses. No need to switch with this lens and I ended up spending less than if I'd bought two.
Pros: Fast / accurate auto-focus, Consistent Output