If you are considering buying a 35mm lens, go with the Sigma. If you have the Canon 35L, sell it and buy the Sigma and then take your lady out for dinner with the leftovers. You won't be sorry. This is a shot I got yesterday, model moving and all. The sharpness is absolutely incredible. This was shot on a Canon 5D mark 2 with natural light.
Click the Full res link to see the entire image yourself! Click it the image again to zoom in.