Got tired of the run around about the Tamron 150-600mm here in Canada so I bought the Sigma 70-200mm f/2.8 os lens. So far all I can say is 'Wow"... I am not a pro so I am sure that they would find this lens not as good as the Nikon version but I just couldn't see paying $1000 more for the Nikon one. I may still buy the Tamron IF it ever gets to Canada but I like the Sigma. Any other input from anyone on that lens. I use it on a D5200...