It is not "impossible" to get accurate focus with a manual focus lens. It's just challenging, and then not in all circumstances. Once you get familiar with the system and lens performance, I think manual focus will become workable in a lot of cases. I've tried manually focusing some of my FA lenses just to see how good a job I can do. I've had some misses and some hits. Hyperfocal focusing works okay, and a combination of focus bracketing or double-checking via digital DOF preview or image review works when I have time with relatively static subjects.
I also have an "A" 120mm Macro coming next week. I plan to use it for macro work, where I would never use autofocus anyway. I don't expect to have any trouble with it. I also recently got ahold of a 67 105mm f/2.4 and it works well manually focused when I have time to dial in or when I'm really paying attention.
Chris Willson (Travel 67) seems to be doing a bangup job with this combination.
We get used to all the modern digital and electronic aids to photography, but people did well without them for a century and a half. Sure, more capable tools are better in some ways. But to my mind it's more a matter of convenience and fine tuning the last few %, not good vs. poor or possibility vs. impossibility...