Ken Rockwell (kenrockwell.com) does some in-depth reviews of cameraas and lenses. He likes the Canon 10-22mm if you have a Canon DSLR. Otherwise he likes the Tokina 12-24mm for build quality and speed. He thinks the Sigma feels cheaply-made and is a little less sharp. Check out his full comparisons here: http://www.kenrockwell.com/tech/digital-wide-zooms/comparison.htm