Zach at Lensrentals.com has completed his review of the brand new Sigma 24-70mm f/2.8 OS Art. Zach came away impressed with the lens, but maybe not impressed enough to buy one.
From the review:
Much to my surprise, I fell in love when using this lens. However, that love I felt was for the focal range itself and not the lens. In short, 24-70mm is a fantastic focal length and makes for an exceptional all-around lens to use on the go. And by all accounts, Sigma does a good job showing off this focal length. However, Canon and Nikon both show it off better, and so when I’m looking for a 24-70mm lens to use as my next all around lens, I’m opting for the Canon EF 24-70mm f/2.8L II over the Sigma 24-70mm f/2.8 Art Series. Read the full review
I haven't use the lens yet, but I look forward to doing so in the future.