I don't have a huge problem with manual focusing, even with standard screens, but I know some people do.

However the new Zeiss lenses - http://www.bobatkins.com/photography/reviews/zeiss_for_eos.html - have electronic compatibility with EOS bodies, so the "green dot" focus confirmation light in the viewfinder will operate and the confirmation "beep" will sound. So it's just like manually focusing a Canon EOS lens. You can use electronic focus confirmation rather than depending on the viewfinder image.

I'm not really 100% sure why people would buy manual focus lenses which are more expensive than their autofocus Canon counterparts, but I'm sure some will claim improved image quality. The Canon 50/1.4 , 85/1.2 and 85/1.8 lenses are not known for their lack of sharpness. I suppose if you are intending to make 24" x 36 "prints then any improvemnt in image quality would be welcome, but for the vast majority of photographers who don't make large prints you have to wonder if the difference will be noticable. Even if corner and edge performance is better wide open, the shallow DOF at f1.4 probably means that nothing in the corners of the frame will be in focus anyway!

It will be interesting to see the results of comparative lens tests. I'd be happy to do such tests myself, though I suspect that getting loaner copies of the lenses for review may not be easy.