I just finished watching DimeCast #15.  It completely blew my mind.  Part of me really likes the elegance of the syntax of using Linq to query the FS.  The rest of me can't imagine the performance of joining files to directories in such a manner would be efficient.  I need to dig in and do some side by side comparisons and get to the bottom of this.  Sounds like the makings of an in-depth blog post.