p.s. Almost forgot... much more important than the "logical fragmentation" is "page density" (that % of page fullness thing) and rebuilding stats.  For GUID clustered indexes, don't worry about page density unless they go less than 68%.  The "Natural Fill Factor" for GUIDs over time pans out to about 69.5% and all pages will eventually be filled and split because of the random nature of the Type 4 GUIDs used nowadays.