I did return the sigma lens to the shop and got a full refund which I used towards another lens, a 70-200 F4 L usm. I want to buy another wide angle lens but the price of the canon is disturbing, $1200 versus the sigma or $750 aus. At this point I suspect I had a below average copy of the sigma and I am thinking about buying another one, hoping I get a better one next time as other people who have bought this lens have had much better results than I have and virtually all of them have said that the quality control of sigma is very hit & miss.
If you buy the sigma, go to a shop that you know and trust and is prepared to refund/exchange a faulty/bad lens and try it out in store if you can.
