I think "no one" is a fairly tall claim: They are well-used on all the operating systems that do support them. Mind also, "old POSIX ACLs" came from a POSIX dr

I think "no one" is a fairly tall claim: They are well-used on all the operating systems that do support them. Mind also, "old POSIX ACLs" came from a POSIX draft: they never made it into POSIX. While being an extremely simple expansion of the Unix modes, they are only ever additive and do not support fine-grained permissions that NFSv4 allows for. They're sometimes better than the standard mode bits, but they very often come up short of being useful in the real world.