Too bad the longest focal length on the Sigma is too short for me! I had a 17mm lens and found it hardly useful, especially on the street. Even my 24mm Nikon lens (which was made in the '60's and does not have any barrel distortion that I can see, not to mention that it is tack sharp) is too wide for me most of the time. I can't imagine I would ever have a use for that lens, and definitely not for street photography.
The only wides I have seen any noticeable barrel distortion on have been zooms or vari-focal lenses. But as I said, I am not comparing to lenses in the 12-24mm focal length range, but to more standard wides like 28's and 35's. And one example does not disprove my general point.