Hi Hilary.
We have a good sticky in the main WW forum with all you should need to know about the Wendie Plan!
http://3fatchicks.com/forum/showthread.php?t=99187
It's a good tool to use for some people, as you said, especially when they hit a plateau. If your losses are going perfectly fine and you are working the program as intended, you may not need to bother with mixing things up. But, it never hurts to try new things