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What's wrong wth the AF-S on current X bodies, Rico?
Plenty. It appears to be a combination of several factors. Some are normal (like stopping down in bright light, which reduces AF accuracy), but I also suspect firmware issues with PDAF/CDAF hybrid AF and at least some lenses. Fuji knows about this for quite some time, so I assume they have fixed or mitigated at least some issues silently with recent firmware updates. However, I don't have the nerve to retest everything after every new firmware version, so I simply use MF when it is useful.
As for AF-S, I usually use Instant-AF when stopped down, which is often more reliable. Also, AF-C appears to be pretty reliable and is now an alternative even with subjects that don't move around. I will do new tests when the rumored X-H1 is here.