The first beta of Hibernate 3.5 with JPA 2.0 support has been released on Sourceforge. It's also available as maven2 artifact from the JBoss maven repository. As Steve Ebersole mentioned most of the APIs have already been implemented.
Some know limitations for this beta include:
Additionally, initial support for "fetch profiles" has been added in this release. Currently only join-fetching is supported as a strategy in fetch profiles
- Some of the 'metamodel' APIs are still unimplemented, specifically differentiating between declared attributes and attributes (same wording as java.lang.reflect). The getDeclaredXYZ methods simply return null in this release.
- 'criteria' query building is fully implemented aside from defining subquery correlations, to the best of my knowledge and current state of the spec. However, compiling criteria queries is unimplemented scheduled for the next release.