All these discussions prompted more and more comparison reviews between those Zeiss manual lenses and their OEM counterparts with fancy zoom, AF, and what not.
Ben Horton over at photocinenews just published a comparison review between a few Zeiss lenses and their Canon counterparts. He sums up the Canon L lenses pretty well “...the 22 megapixel sensor can capture more detail than the Canon L lenses can give it” “Using standard Canon glass, any sensor larger 16 megapixels is a waste.”, and he describes Zeiss lenses as “The Zeiss image has much more contrast, color, and less blur when viewed at a 1/1 ratio. The Canon image is soft, and darker (even though I used the same exposure) as well as a little bit gray.” “Zeiss lenses are better. The Canon lens doesn’t have the clarity, contrast, or saturation that the Zeiss lens has.”
Take a look at his review here.