The Restlet team just announced a new release. Amongst the new features is support for JAX-RS, see an example here. With the RI (Jersey), Apache CXF, and JBoss RESTeasy, that makes a total of four implementations currently underway. The feedback we're receiving as a result of these parallel implementations is proving very useful and I'm grateful for the all the good input we've been getting.
The graph below shows the monthly totals for emails sent to the dev, users, issues and commits mailing lists for both JAX-RS and Jersey.
As you can see, traffic on the lists has picked up quite a bit over the last few months and a good proportion of the increase is due to the additional implementation work flushing out issues. We've also been working through our issues list with a view to publishing a JCP public review draft in the not too distant future.