I am planning to upgrade on 50mm lens .
The dilemma is between canon 50mm 1.4 vs sigma 50mm 1.4 vs zeiss 50mm 1.4.
Some of the pros and Cons I have read from reviews is

Zeisss
Cons : manual focus, pics are soft at wide open
Pros : superior optics.

Sigma
Cons: trail and error as it has some focus issues ,
Pros :Released recently in 2008 ,sharp and great bokeh

Canon
Cons : Old technology, not sharp when wide open
Pros: Cost and good photos.

Thanks in Advance