First, I think the rule will accomplish that. I assume that currently, the client makes a request to www.example.com/, the server redirects them to http://www.example.com/home/default.htm, the browser follows the redirect updating the address bar to http://www.example.com/home/default.htm and displays the default.htm content. So this iRule prevents the server from having to redirect the client from / to /home/default.htm by rewriting the URI before the request is sent to the server.
If you use your original approach to rewrite the application's redirect from http://www.example.com/home/default.htm to http://www.example.com/, the client will probably get redirected in a loop from http://www.example.com/home/ to http://www.example.com/home/default.htm and back.
Out of curiosity, why are you trying to do this? Is it for ease of use or based on some security concern?
Aaron