After quite some time using JPA (Hibernate implementation), trying to map what amounts to legacy (well, that's too harsh--probably should say 'traditional') db schema to JPA entities, which resulted in hours, nay, days of frustration, I finally feel like I understand how to use JPA with Hibernate (though some of the quirks I could do without, or maybe have features implemented).
[Side note: I was reminded that Hibernate was not a cure-all for object access to the database, but that it implemented a subset of everything that could be done. The first thing that comes to mind that is similar is Ruby on Rails and ActiveRecord--you do it their way if you want to use it.]
It all came to me (understanding the docs, etc.) when I finally (!!) decided to let Hibernate build the schema for me. Now it is much clearer.
Should have done this in the beginning.