The problem with the Samyang is not the lack of auto focus. Somehow we managed to focus lenses manually for a couple hundred years (though personally I only used manual focus lenses for around 25 years). AFAIK, it's still possible. You might want to get a focus screen that makes it easier, but that's possible, too.
I'm not saying AF isn't nice. It is. It's faster and more accurate than I ever was, manually focusing lenses. I'm able to get shots with AF that I never could with manual focus.
The bigger issue is probably the manual aperture. That makes it slower to operate the lens, having to stop it down manually, doing "match needle" metering. And at smaller apertures your viewfinder will be dim so harder to focus and compose.
The Zeiss ZE may be manual focus, but are still auto aperture (maintained at their widest until the moment of exposure and controllable from the camera).
The Samyang (and their Rokinon, Bower and Vivitar cousins) are all manual, aperture and focus. Focus isn't difficult on their ultrawides such as the fisheye and 14mm, thanks to the gobs of depth of field inherent in those lenses. It's a bit harder with the 35mm and even more challenging with the 85mm. It's got to be especially tricky the 500mm mirror lens (fixed f6.3 aperture).
i will have it again, i really liked it
the colors are just very nice, and no PP involved, as i suck at that! these are handheld, as well! i feel that Zeiss are very unique in their offerings, and their ability at close focus are awesome!! 
