Take a look at this article on Double Metaphone in T-SQL:

http://www.windowsitpro.com/Article/ArticleID/26094/26094.html?Ad=1

The author provides a T-SQL version of the source code. In my preliminary tests, my port of Double Metaphone to the SQL 2K5 CLR runs over 8 times faster than this T-SQL Code.

For me, getting 8 hours worth of T-SQL processing done in 1 hour is a pretty good and "proper reason for using CLR."