Good article. Very informative. On performance, if I use a GUID as a Primary Key with a clustered index, won't that require the database to constantly 'reorder' the data since a clustered index determines how the data is stored physically. Perhaps a larger fill factor is needed to help alleviate these concerns?
Example: If I use an integer for my PK in the orders table, new orders are always appended to the end of the table. Order 1,2,3,4,5 are all added in sequetially. With a GUID, I have no idea where an inserted row will end up physically in the table.
Thanks for the info Andy!