If the new Tamron 16-300 lens is as good as the old short lived Tamron 18-250 I have, it should be on everyones short list that's looking for a long zoom.
The reason for the "just stinks" comment..., I have both Canons 35-350L and the 28-300L lenses also.
With either of these three mounted either on my old 50D or my newish SL1, the "old" Tamron 18-250 outshines both of Canons L lenses in sharpness..! I thought I was seeing things, maybe a bit off in viewing my pictures. So I did some non-scientific experiments with both cameras and all three lenses and two computers. All three show nice colors, no I didn't look for purple fringing. But in the center 80 or 85% of the frame...Tamron wins by a landslide.
As far as front or back focus, I don't see anything percepetable in any of my shots so the Microfocus might not be of much help....though I haven't ruled it out.
All I can say is...despite the timeframe of the design and builds, and the money difference in the three...Canon should be ashamed.
And yea...it stinks that I've spent a LOT of money on Canons HIGH END lenses just to be outshined by a 500 dollar (about) third party lens special.
Here's to looking foward to the 16-300 Tamron.