Using aclitem[] at application layer

Hello,

In an attempt to implement ACLs at the application layer (for resources stored outside of the database), I am evaluating using aclitem[] as a column type. All the functions I would need seem to be in place: aclcontains, aclexplode, aclinsert, aclitemeq, aclitemin, aclitemout, aclremove, but they are conspicuously missing from the documentation (http://www.mail-archive.com/pgsql-patches@postgresql.org/msg03400.html), so I wonder if there are any caveats or hurdles which would make me consider writing my own type.

From a cursory examination, it looks like the limitations would be:

1) roles must refer to postgresql roles (that's fine for my case)

2) permission options are hardcoded to "arwdDxtXUCTc" (not so great)

Are there any other problems I would encounter?

Cheers,
M