Comments about Sigma Sigma 70-200mm f/2.8 DG Macro HSM II Auto Focus Telephoto Zoom Lens Kit, for Nikon AF-D with Tiffen 77mm Photo Essentials Filter Kit, Lens Cap Leash, Professional Lens Cleaning Kit:

I use this lens on a Nikon D300 and it is great af-c and 3d tracking make action shots easy. I recommend a monopod because this lens is heavy and an extended shoot will make you wish you had ate your Wheaties. The images are sharp even at f/2.8. I read several online reviews saying the Tamron has better IQ while the Sigma focuses faster. I haven't used the Tamron but did try the Nikon 70-20mm F/2.8 vr and for less than half the price I like the Sigma better. If the Sigma was 3/4's the price of the Nikon the Nikon would win out, but at 1/2 it's on my camera. Don't get me wrong the Nikon is nice just not [$] nice compared to the >[$] Sigma.