I went to my local camera shop to see about a new lens. I would like to do some simple portraits and sports photography. The lens that the store suggested was the Sigma 2.8/F 70-200 APO EX DG Macro. Has anyone used this lens before? If so do you like it or not like it? I played with it some in the store and I enjoyed it very much. It was very quick and quiet. Thank you for your help.