I have a 1Dsmk3 and 5Dmk2 - no issues focusing with the Zeiss 21mm. I use it mostly for landscapes, so often trust on the hyperfocal range anyway.
Now, the new 135 f2 it's different story. Got it as a rental last week, and has a smooth barrel movement, but indeed is not a lens for street, or anything requiring fast action (as in snap the shot quickly).
It's great for landscapes, close-ups, portraits and sure you can use in other creative ways, but if you use it wide open, the DOF is narrow enough to ending missing the shot.
Beautifull crafted lens, heavy, with a solid feel and really smooth barrel movement. But at this range, I rather have the 100 MP or maybe the ef 135L - still have to try this one.
Depends on the intended use you have for it - the bokeh is beautiful, and produces nice sun stars too