Ok, I'll start the ball rolling.
I own the Canon 135f/2, I admit up front I have never owned a Zeiss Lens, but I've heard/read great things about them, but, the Canon 135f/2 is just a superb Lens, would the Zeiss be any better do you think ?? I understand the Zeiss lenses are Manual Focus, and for me although not a Killer, I have the 17 24 TSE Canons, it does make life a little more difficult, I sold my Leica M9 for this reason, lovely camera but the Manual Focus became an issue for me (Age Factor). Si I'm really interested to hear opinions on the Zeiss versus the Canon.