throw in the stabilization and much lower price this lens is certainly worth considering if you don't have the budget for Canon's latest or the Nikon.
It also beats Canon's f/4 offering at a similar price point.
Anyone been using it? How is it working for you.. subjectively?
Other than it's less-consistent across-the-range performance and likely less rugged build than the Canon, I don't see much for drawbacks to the Tamron for shooters who don't need best-in-class gear in this range.
Very very good value compared with Canikon.
IS is awesome and definitely very helpful in a lot of situations especially if you shoot in low-light environments.
Good build quality. Not L grade, but definitely better than average.
Optical quality - very good also. Not the best one, but definitely on pro level. Still I didn't need so far a better quality, speaking practically. If Canon 24-70 MkII would be at the same price I would still choose the Tamron because of the IS. If the Canon would have IS I would pay 200-300$ more for the Canon's MkII quality but not more.
There was some discussion about 'onion bokeh' - the issue is there but way overrated. Till now this issue didn't ruined me any single photo. And I shoot regularly in dim light environments. Same stands with the vignetting at f/2.8 - way overrated on forums. Ok, here you must remember, if you're bothered by this, to not shoot at f/2.8 the sky of the wall or any other monochrome boring composition.
Overall very pleased with Tamron.