I did look at 2.0 when it came out, and I'm under the impression that you still need to write a custom binder. Just now I tried to look it up, but the documentation points to:

http://www.playframework.org/documentation/2.0/JavaJson

which is a 404.

I also don't see a nice way to respond with the appropriate format based on the accept-header...not that you can't write that yourself.