Joe Long, the Product Unit Manager for XML Enterprise Services at Microsoft, talks about the Indigo migration story in this recorded presentation on MSDN. If you weren't at Joe's PDC talk and think you don't have 37 minutes time for this, you can still not afford to miss listening to the prescriptive guidance section starting at slide 60, if you ever have or will cross an application domain boundary with a Remoting, Enterprise Services or Web service call on the current stacks. And now leave here and go there.