I just held and used the Tamron 24-70 VC and 70-200 VC (my dad's on his Nikon D90). The 24-70 is much larger than I expected and build quality is quite nice. It is actually quite intimidating. It's not a lens I would purchase myself (I don't need a general zoom on a DSLR). The 70-200 on the other hand is a beast. The construction is outstanding. I just don't like the hood (feels and looks cheap) and everything is reversed (zoom ring rotation etc).
I don't know if it was fault of the body or the lens, but the 70-200 failed an extremely task of focusing on a relatively large subject, a blue flag flowing with the wind that filled maybe 30% of the frame on top of the garage with a very cloudy sky as the background. It did, however, search for focus again and achieved focus very quickly. I repeated this test and it did the same thing every time, but I focused on a few other subjects at various distances and it was quick and accurate. Strange.
I am partially glad I didn't like the Tamron 70-200 2.8 VC a lot, because I have already decided (and placed a $500 deposit on) a Canon 70-200 2.8 IS II
It sure is a LOT of cash, but a 70-200 is one of very few lenses where I believe little to no compromise should be made (for my use).




