I was just reading the review on his website and saw that he didn't have anything good to say about the build, quality, and stability of the lens. He does say that it's super sharp, sharper than both Canon and Nikon's 35mm professional lenses. I just wanted to check with the people who own Sigma and who has owned 35L at some point in time and see if they think the review is accurate.
The only reason for this lens is price, not quality. If you shoot Canon, the Canon EF 35mm f/1.4 L (about $1,260 after you add it to your online shopping cart) is a huge bargain. It's a proven, fully professional lens far better made than this Sigma, and not much more expensive. If you shoot Canon, get the Canon lens and you'll never look back; the quality is remembered long after the price is forgotten. The Canon L lens is all-metal, and optically superb as well. This Sigma is nowhere near L quality mechanically.
As the ancient proverb so correctly observes, "the poor man always pays twice." He pays once to get something cheap, and then again pays full price for what really wanted in the first place when the cheap thing breaks. How do the rich get richer? By always buying quality. I'd much rather have a used Nikon or Canon 35/1.4 than this Sigma.
I wouldn't buy a Sigma lens because I don't trust their lens' long-term viability (I demand that any lens I buy serve me for about 20 years), but if you can get over my personal problems, this consumer-grade Sigma 35mm f/1.4 DG HSM has the same superb optics as Nikon or Canon's professional lenses.