I just got this lens in the mail today and it outperformed my expectations. Since getting my D3s my older 80-200 just wasn't cutting it with sports on larger fields(HS football), but I can't afford to go drop another 5 grand on the Nikon 300mm 2.8. So researched the Nikon 300mm f/4, Sigma 300 f/2.8, Sigma 120-300mm f/2.8 and the 100-300mm f/4. Obviously I landed with the 100-300. My main reasons being the size(I hate using monopods because it makes getting out of the way quickly much harder) and the added zoom if action started getting to close to shoot at 300mm. This things is much sharper than my Nikon 80-200(which I plan to replace in the next 2-3 months), quieter, and focuses a lot quicker. And the price couldn't be beat. I got it from Allen's Camera(should sound familiar with anyone who knows froknowsphoto.com) for $899. I always regretted my Sigma purchases in my early days and that led me to buying only Nikon, but in this one case I'm beyond happy with Sigma.