Jersey 2.0 milestone 2 is now available. It builds upon the first milestone and adds several new features such as server-side asynchronous processing, server-side content negotiation, improved JAX-RS parameter injection, and several others.
The REST endpoints can be published on Java SE HTTP Server, Grizzly 2 HTTP container, and some basic Servlet-based deployments. It also provides HTTPURLConnection-based client API implementation. Read about these and more about what's new in Marek's detailed post. Of course this is also the future reference implementation for JAX-RS 2.0.
Feel like trying it out? Simply go to Maven Central (of course none of this is production quality at this point). The latest JAX-RS Javadocs and Jersey 2.0 API docs are good starting points to explore. And provide them feedback at firstname.lastname@example.org.