Who is using ACLs in production?

[Anthony Atkielski]

Anyone using ACLs in production on FreeBSD 5.x?  If so, how do you use
them, and what are your impressions?  How do they affect performance,
how reliable is the code, does it really help security, etc.?

I've enabled them on my test system to see how they work.

Also, if someone can tell me why tunefs refuses to enable ACLs on the
root filesystem, I'd appreciate it.  I get

# tunefs -a enable /dev/da0s1a
tunefs: ACLs set
tunefs: /dev/da0s1a: failed to write superblock

I get the same error if I try to set ACLs on just '/', and the error is
the same in both single-user and multiuser modes.  If I mount /
read-only, I can set ACLs and verify it with tunefs -p, but after I
reboot, the ACLs are disabled again.  What do I have to do to enable
ACLs on /?

-- 
Anthony