I'm going to see how it works with PostgreSQL.
My boss loves EJB and it's container-managed persistience, but I'm interested in the more light-weight approach of Hibernate. EJB's learning curve is so steep, I'm afraid to touch it, especially for the simple stuff I've got in mind.
Java Persistence Resources:
Java Persistence Engine (Object-Relational Mapping) by Julian Harris.
Object Relational Mapping Tools by Anthony Berglas.
Announcing Hibernate 1.0 Open Source O/R Persistence Tool by Gavin King plus discussion on The Server Side which includes a number of the criticisms of O-R mappers. It's a little old and it seems that Hibernate has fixed a lot of the criticism.
survey of O/R tools thread on jug-discuss mailinglist.
Torque another approach to O-R mapping, from the Jakarta Project. If anyone is aware of of comparison of Hibernate and Torque, please let me know.
ObJect Relational Bridge also from Jakarta. This implements JDO. I think.