I bought it 2 days ago, and i love it. The AF is reasonably good: i used every single focus point of my 6D, and the pictures were in good focus. Sharpness and contrast are excellent even at the largest aperture. Vignetting is heavy, but it gives some shots a certain look that i like, and it can be easily corrected with post processing. I know 2 days of usage are very few, but i would recommend this lens. The only real alternative to the Sigma is the Canon 35/2 IS: slightly less sharp, slower aperture, but the AF should be as good as any other Canon lens, it is stabilized, and quite a bit cheaper than the Sigma. I see no point in getting the Canon 35/1.4, its cost is almost double the cost of the Sigma.