Thank you for posting this nice little script.
I've just found one little issue when running in my environment.

I call named instances 'MSSQLSERVER1', 'MSSQLSERVER2' etc.
When running your script the result in the 'SQLServerInstance column is 'default1', 'default2' etc.

A solution to replace instancename on the default instane only, could be using CASE instead of REPLACE:

,SQLServerInstance =
         CASE InstanceName
            WHEN 'MSSQLSERVER' THEN 'default'
            ELSE InstanceName
         END

// Christian