Got my Sigma in the mail yesterday. So far I really impressed with this lense. Coming from using a tamron 28-75, I think that the sigma is a better lense for crop camera. However, I have noticed a kindof grinding noise with the autofocus when its trying to lock focus. Is this normal? It seems pretty dang sharp on the long end at 2.8 but I've noticed that its pretty soft on the wide end at 2.8. So far I like like it. I think I'm gona miss the extra reach of the 28-75 but I purchased an canon 85mm 1.8 for the long end.