This part of your comment concerns me. If you consider the 24-105 too heavy, then the Tamron lens should be out of the question for you, since it's about the same or a bit heavier.

All I can say is that I love it, and it has become my workhorse lens. I travel a lot and even though the Canon 5DM3 with the Tamron lens are a bit heavy, it's worth it, knowing that I can get just about any shot I need.

I post process in Lightroom and have not found that the lens is too soft at maximum telephoto. It might be, if compared to the Canon version. But so far, no one has told me that any of my shots needed better focus.

Bottom line, get the Tamron. You won't be disappointed. Unless weight is your most important criterion.

I hope these focusing issues are not significant because I just ordered this lens for the specific purpose of travel portability. I have five L lenses and considered the Canon 28-200 but the price and weight were more than I wanted to deal with. I have found that relying on the 24-105 as a walk around lens is problematic at times with limited reach on a FF 5DIII although the images are flawless. I am headed out on a big photo trip next January to SE Asia and hope this combo will be the answer to a perfect walk around solution. The lens will be delivered on Monday and I'll try and report back to this thread after I check it out.