mount_unionfs(8)

[Andrew Berg]

What is the state of unionfs? There was apparently a big reimplementation of it
that was merged in when 7 was -CURRENT, but there is absolutely no mention of
this in the man page, which is dated November 30, 2006, and has a big scary
warning:
THIS FILE SYSTEM TYPE IS NOT YET FULLY SUPPORTED (READ: IT DOESN'T WORK)
AND USING IT MAY, IN FACT, DESTROY DATA ON YOUR SYSTEM.  USE AT YOUR OWN
RISK.  BEWARE OF DOG.  SLIPPERY WHEN WET.  BATTERIES NOT INCLUDED.

This leaves me highly confused. Was the man page really never updated in the
last 7+ years? Is unionfs as it is in 10.0-RELEASE stable and functional? If
the man page really is outdated and the big scary warning is not appropriate,
what are the valid options, and what are the known bugs (if any) that should be
noted in the man page?