As I write this, the Zeiss 135mm f/2 APO-Sonnar is IN STOCK at B&H* for Canon.
Canon users in particular should study the comparison of the Zeiss 135/2 APO-Sonnar to the Canon 135mm f/2L.
See my in-depth review of the Zeiss 135mm f/2 APO-Sonnar, including coverage and comparison with Nikon and Cano lens, and even performance on the Leica M Typ 240.
Readers often inquire what the “best” lens is. This is usually a complex question. Not so with the 135mm f/2 APO-Sonnar: the Zeiss 135mm f/2 APO-Sonnar is the highest performing lens in the entire Zeiss ZF.2 / ZE lens line, indeed one of the highest performing DSLR lenses available today (maybe the best), and is thus a must-have for any serious shooter.
* Bookmark the Zeiss Gear page for in stock status in general; the buttons are updated twice per hour with in stock status, so you can see at a glance what’s in stock or not.