We're using this extensively in openacs4. If you download the latest code, you can find the tree encoding table and some tree-utility routines in openacs-4/packages/acs-kernel/sql/postgresql/postgresql.sql. For corresponding trigger routines look at openacs-4/packages/acs-kernel/sql/postgresql/acs-objects-create.sql - specifically look at the acs_objects table definition and its associated triggers.
With regards to inheritance, we looked seriously at prior to starting the opeancs4 porting activities and we opted not to use it because it was deficient in serveral areas.
