The problem with unplugging the ORM or inter operating is that the 2 biggest ORM frameworks are implemented such that they don't support composite primary keys

The problem with unplugging the ORM or inter operating is that the 2 biggest ORM frameworks are implemented such that they don't support composite primary keys and have stupid requirements like having an auto increment column called "id" on every table (including tables used as part of a many to many relationship!!). As far as I know Doctrine 2.0 absolves a lot of these problems but I've not used it yet.