I have recently set up a website that uses Orchard 1.5.1, I attempted to use an application called Blogsy to publish content from my iPad however the application was generating an error when using the xmlrpc. After some investigation and an exchange of emails between myself and the team at Blogsy they identified the problem. It turns out that their application is looking for the xml declaration <?xml version="1.0" encoding="utf-8"?> in the response message from service call. After looking at the code for the XmlRpc -> HomeController I noticed that the XElement is converted to a string and output as content. I modified to write to the response stream directly, this way the xml declaration is included in the response.

        var content = _writer.MapMethodResponse(methodResponse);

        this.Response.ContentType = "text/xml";
        content.Save(this.Response.OutputStream);

Is this something that could be fixed? There are only a handful of applications on the iPad for blogging. I think it would be good if Orchard was supported.