The Indigo Windows Communication Foundation folks have decided to let the code do the talking in showing that they are serious about supporting Plain Old XML over HTTP (POX) and RESTful Web services. You can download the WCF RSS Toolkit and try it out yourself. If you are like me, you may not have all the requisite beta bits installed to run it, in which case you can peruse the WCF RSS Toolkit Code Samples which show how straightforward it is to produce RSS or Atom using WCF. 

Sam Ruby has asked whether the WCF RSS Toolkit supports ETags which is really a proxy for asking whether WCF supports manipulating HTTP headers directly. In my conversations with WCF folks like Yasser & Doug, the answer is that although the WCF RSS Toolkit doesn't support ETags that this was due to time constraints than any limitations in WCF. The Windows Communications Foundation will support service enpoints directly interacting with HTTP headers and HTTP methods. So one could build a real-world RSS endpoint or even a WebDAV or Atom Publishing Protocol end point with WCF.