In terms of JPA 2, its really easier to start talking about things not yet implemented :) The set of missing features are defined by the unresolved subtasks of the following 2 Jira issues:
The still-to-be-implemented features are mainly certain aspects of
derived identity support and support for embeddables with associations.
Check out the release details for the full list of changes.
As always, please report any issues to Jira and come visit us on IRC or the forums if you have a usage question.
We are getting so close folks! Great work.