I must admit I am somewhat ambivalent to storing XML in a relational database.

If I am going to store XML data it is because I want to retrieve it in entirety. Being able to search an XML document within a relational database engine strikes me as a kludge. If I wanted to search the content of an XML document I would have shredded into tables. It is one of those arguments where you either support "The Judean Peoples Front" or "The peoples Front of Judea"

My method actually used the source of sp_spaceused minus some of the branches.