Dustin has completed his review of the Sigma 50mm f/1.4 DG HSM Art for Canon Rumors. This follows the other 50mm offerings from both Zeiss and Canon.
Dustin came away impressed with the Sigma offering, but had the same concerns as others when it came to autofocus performance. However, the other 50mm offerings out there aren't perfect either. The Zeiss Otus doesn't have AF and the Canon 50mm f/1.2L can suffer from focus shift which is very frustrating for some photographers.
All in all, Sigma has made a major breakthrough in creating a large aperture prime with world class optics that is in a price range that most professional and many amateur photographers can afford. While the stated “target” is the Zeiss Otus, there will actually be fairly few photographers that are cross-shopping these two lenses. The Otus is still the optical king (and this goes beyond chart testing) and enjoys a certain cache that Sigma can't touch. But the Sigma is a far more practical lens for most photographers, as most photographers need autofocus for their work.
Read the full review | Sigma 50mm f/1.4 DG HSM Art: B&H Photo | Adorama | Amazon