I was recently at a seminar where a Nikon pro/rep was giving a talk. They strongly suggested that Nikon owners should only shoot with Nikon Nikkor lenses. The reason he gave was that Nikon lenses, specifically the glass in those lenses, are optimized for Nikon body sensors. I need a 70-200mm f/2.8 lens and the 2700 price tag is just a touch out of my range. I was really scoping out the Sigma 70-200 f/2.8 DG OS HSM, which hasn't come out yet. After hearing this new information though I've become hesitant and wondering if I should wait to save some more cash. I've never owned anything but Nikon lenses and just wondering what others have experienced.