Hi Rob,
I don't know for sure what Beat has up his sleeve for ACL, but right now I'm using JACL for custom permissions, which is an open source solution that's working okay for me.
User Reviews for the extension are mixed because it's a hack of core files, and must be maintained as such. You can get the Joomla updates from the JACL Home Page however, and that saves some headaches and hassles.
I need the ACL flexibility on one of my sites, so I deal with the inconvenience of having to maintain hacked files. It would be nice if CB could handle ACL customization and seems the logical choice, since CB is something of a user shell... but how much can a person ask of CB?
Now watch -- Beat will go and shock me and have all that coded in. LOL!
:side: