Whenever this topic comes up, I say "It Depends" and refer folks to the following video. It might change your mind about the use of IDENTITY columns as the clustered index, which should not be necessarily confuse with what the PK should be. There's more to it than just "logic".
http://technet.microsoft.com/en-us/sqlserver/gg508879.aspx
--Jeff Moden
Change is inevitable... Change for the better is not.