Just published on MSDN: Xml Best Practices for Microsoft SQL Server “Yukon”.
This paper provides guidelines for XML data modeling and usage in SQL Server "Yukon." The paper is divided into the following two topics:
Data modeling
There is more than one way of storing XML data in SQL Server "Yukon"—for example, using XML data type and XML view of tables. This topic provides guidelines for making the appropriate choice for modeling your XML data. This topic also covers indexing XML data, property promotion, and typing of XML instances.
This topic discusses closely-related features, and suggests appropriate use of these features. Some examples are provided to illustrate the ideas.