Image quality results have been added to the Tamron 70-200mm f/2.8 Di VC USD G2 Lens Review.
I think that you are going to like what you see here. Check out the Tamron G2 vs. Canon IS II comparison.
B&H has the Tamron 70-200mm f/2.8 Di VC USD G2 Lens in stock (Nikon mount coming very soon).