Check the specs out. As an EA, there are some relatively big holes in the specs; for example, the JAXB 2.0 spec is only hinting at the addition of updateable partial binding, which I think is a very big improvement. There are a number of other key improvements, including:

• Integration of the two specifications: you now will be able to use the full JAXB machinery to do data-binding on JAX-RPC invocations
• Completion of much of the customization features in JAXB that were hinted in JAXB 1.0.
• Updateable partial binding, where a portion of an XML document can be bound to Java objects, which can then be updated and then converted back to a document.
• Support for asynchronous messaging in JAX-RPC.
• Support for other transports to HTTP in JAX-RPC.

There are other features; attend the JavaOne sessions on these topics to get more details, and I'l invite Marc, Roberto, Sekhar and Joe to present at some technical forum in the near future.