I'm testing resteasy for our rest-service communication. Very promising, and I look forward to the first official release. Since we're using Internet Explorer I ran into the following problem (Tested with beta-8, beta-9 and RC1. Code from RC1.):

The org.jboss.resteasy.plugins.providers.AbstractEntityProvider always return length -1. This causes the Internet Explorer to discard the XML. These are the response headers (from Firebug):
Content-Type text/xml;charset=utf-8
Content-Length -1
Connection close
Server Jetty(7.0.0.pre5)

If I leave the Content-Length to the webserver, and comment out line 441 and 442 in org.jboss.resteasy.core.SynchronousDispatcher:
// long size = responseInvoker.getResponseSize();
// response.getOutputHeaders().putSingle(HttpHeaderNames.CONTENT_LENGTH, String.valueOf(size));

I get this response ::
Content-Type text/xml;charset=utf-8
Transfer-Encoding chunked
Server Jetty(7.0.0.pre5)

Now the xml works fine in both FF3 and IE7.