I have been comparing this lens for about a month against the Canon 24-70 F2.8L and my final analysis is that the Sigma shoots better pictures! I don’t care what you read on other reviews this lens is truly a steal at $400 I shot tests of newsprint with both lenses and I believe that this lens is sharper at 2.8 than the Canon version! I thought that maybe I had a bad Canon lens so I took it back to the store and exchanged it with another one and to my amazement the Sigma still outshined the Canon! So I returned the Canon and kept the Sigma. I suggest you try it for yourself just be aware of the store’s return policy. Using a tripod set your ISO as low it will go (I shoot with a 10D so mine was set to 100) and take pictures of news print at all apertures and focal lengths a bit tedious but the results will amaze you!
Or…. You can just take my word for it and purchase this lens and save your time and money and just go shoot… I think that is what this is all about isn’t it? I mean Alfred Eisenstadt, the legendary LIFE Magazine photographer, didn’t believe in other people's lens tests. He tested his own new lenses by using them. If he liked it, he kept it.
Amazingly, Eisenstadt didn't think he needed someone else's lens test of someone else's lens to take great pictures. All he succeeded in doing was help define photography this century. Maybe he was too busy taking pictures to care what someone else thought about his lenses. How weird. Misplaced priorities, I guess.