I have the Tamron 70-300 VC for about a year and am more than satisfied with this lens on my Canon 1000D. Previously I had the 70-300 IS USM Canon with which I was not satisfied. And in hindsight, I can now indeed confirm that the Tamron is superior to the Canon in all respects. It is sharp over the entire focal length range, here left my Canon strong especially from 250mm to. The focus speed is faster than that of the Canon. As also is still the price of the Tamron less, in my opinion, speaks for users of a Canon DSLR everything for Tamron 70-300VC. The build quality is also excellent by the way.
Greeting
Tobias