Optimization suggestion for hierarchical data

I recently stumpled upon an interesting way to do recursive with CTE.

Links:
http://blog.sqlauthority.com/2008/07/29/sql-server-sql-server-simple-example-of-recursive-cte-part-2-maxrecursion-prevent-cte-infinite-loop/

http://blog.sqlauthority.com/2008/07/29/sql-server-sql-server-simple-example-of-recursive-cte-part-2-maxrecursion-prevent-cte-infinite-loop/

http://blog.pengoworks.com/index.cfm/2007/11/30/Finding-the-path-in-a-hierarchical-tree-in-MSSQL-2005

So the sql will look like this:

<code>

WITH CategoryTree AS
(
    SELECT
        CategoryId,
    ParentCategoryId,
        CONVERT(VARCHAR(MAX), theRow) AS thePath,
        CONVERT(BIGINT, 1) AS prevNumer,
        CONVERT(BIGINT, 0) AS prevDenom,
        CONVERT(BIGINT, theRow) AS currNumer,
        CONVERT(BIGINT, 1) AS currDenom
    FROM
    (
        SELECT
            CategoryId,
      ParentCategoryId,
            ROW_NUMBER() OVER (ORDER BY DisplayOrder) AS theRow
        FROM [Nop_Category]
        WHERE ParentCategoryId = 0
    ) y
    
    UNION ALL
    
    SELECT
        y.CategoryId,
    y.ParentCategoryId,
        y.thePath + '' + CONVERT(VARCHAR(MAX), y.theRow) AS thePath,
        prevNumer = y.currNumer,
        prevDenom = y.currDenom,
        (y.currNumer * y.theRow) + y.prevNumer  AS currNumer,
        (y.currDenom * y.theRow) + y.prevDenom  AS currDenom
    FROM
    (
        SELECT
            e.CategoryId,
      e.ParentCategoryId,
            x.thePath,
            x.currNumer,
            x.currDenom,
            x.prevNumer,
            x.prevDenom,
            ROW_NUMBER() OVER (ORDER BY e.DisplayOrder) AS therow
        FROM CategoryTree x
        JOIN [Nop_Category] e ON e.ParentCategoryId = x.CategoryId
    ) y
)

SELECT
    CategoryId,
  ParentCategoryId,  
  LEN(thePath)-1 as [Level]
  /*
    currNumer AS startNumer,
    currDenom AS startDenom,
    currNumer + prevNumer AS endNumer,
    currDenom + prevDenom AS endDenom
  */
FROM CategoryTree ORDER BY thePath OPTION (MAXRECURSION 20)


</code>


It is very fast, and i'm sure it' beats the current implementation (currently it's being done in BL). Also a function like this would simplify methods where you want to display all products and categories greatly (you can just have one category repeater and one product repeater, no need for nesting....which is a pain in a repeater)