Since Tamron SP series launched, I see no reason to invest in L lenses. There are now the 17-50 (for Crop), the 24-70 and the 70-200 now in my possession. All of these lenses provide out of the box excellent results, even under adverse conditions.
Technical details have been posted here already sufficiently, I see no reason to repeat that.
Anyone who buys a lens 2,8'er who wants also use f / 2.8 ... at first I was a little unsure whether because the Tamron delivers clean at 200mm and maximum aperture. In short, it delivers damn clean. The Canon counterpart like it can "clean", but this one will have to seek the lab. In "real life" 'provides the Tamron ambitious photographers everything your heart desires to become more than a fair price.
More 70-200 definitely does not need it! At FF, as well as at the Crop "WOW effect" provides an urgently and unconditionally.