With the upcoming new release of the JBoss AS package in Fedora you'll be able to use both the Hibernate 3 and OpenJPA JPA providers. The reason why I'm enabling this for you is that we still don't have Hibernate 4 packaged, which is a pity since Hibernate 4 is the default JPA provider in JBoss AS 7. If you want to help us with it, please consider reviewing the Gradle package.
I crafted a small application that shows how to use the two new providers. The full source code is available from my GitHub account. This application uses JSF and CDI in addition to JPA. And yes, I use both JPA providers at the same time.