I read that review before I made the purchase. I tend to read all reviews before spending dosh.
Thing is, if not the Sigma then what?
There's no competition, not at the focal length and certainly not at the price. I'm sure the Nikon 12-24mm is optically superior but at nearly £1000 it's a moot point. When I was looking for a wide-angle I initially bought the Tokina 12-24mm, which I think on balance was optically superior, although due to a manufacturing defect with the one sample I had I ended up returning it and opting for the Sigma in it's place. I have never once doubted that decision.
Another thing to note, 2mm at the wide end really is a big jump, believe me. Nothing else comes close. You see that picture I have of the tree which I named (rather bizarrely in hindsight), Afro? I was no more than 15 feet from that tree. Which is just as well as any further away and I'd have been swimming. That's the difference 2mm can make.
P.S. You have mail.
Various lenses, SB800 & Manfrotto 190 with 460MG head