I do agree with Gail Shaw's articles about the indexes, but I did not read where he suggested to make the clustered unique index on the unique identity column of a table. Making the clustered index on the logical, unique, as narrow as possible columns stored at the beginning of the table, where these columns are ever increasing in value with new inserts, and not changing in key values for the existing rows... in my humble opinion is the right way to choose the clustered index. I do have unique non-clustered indexes on identity columns when I need to use those values to retrieve row(s).

By organizing the logical data together, it makes it efficient for windows and reports retrieving the data by the logical order to be more efficient in data access instead of jumping all over the disk to get a couple thousand rows, they are neatly stored by their buddies.

In my understanding this is the concept of clustering indexes, not only for MS SQL Server, but many other relational and non-relational databases.