All extended stored procedures mentioned in the article are well known to most of the people working with SQL Server for some years. They have been discussed many times in SQL server books and on popular SQL Server websites. Google search on "undocumented sql server stored procedures" returned 89,000 web pages. xp_FileExists for example is discussed at sqlservercentral, developersdex, databasejournal, sqlteam, dbforums, etc. The article lacks novelty but may be useful for some community members. That's why I rated it as 3-star.