Have you recently tried to migrate an existing ASMX Web service to Windows Communication Foundation, and discovered that the complex types you've so lovingly hand-crafted for the XmlSerializer don't work the way you expect? Are you having to resort to MessageContracts to obtain the serilization behavior your desire?

I recently wrote a lengthy post over on my blog that outlines a namespace problem when WCF serializes complex types that live in a different XML namespace than the Web service itself and a work-around provided by Dino Chiesa.