Thanks for releasing the code. Some initial feedback, based on the description. I haven't tried the module(s) yet.
Name. Why not Pg::Object and Pg::Object::Simple.
The description leads me to believe that PGObject would be better as a Moose role. Especially "Most developers will want to use more functional modules which add to these functions." and the note about state handling.
PGObject::Simple looks like a class consuming that role.
Just a thought, as I can see that LedgerSMB uses Moose.