Basically I agree with jclark58's post.
But when a business user deals with customers in different languages, it is a REAL PLUS to be able to switch the application's language in use.
For ex., I speak with my customers in their own language, either in german, french or english. And I can tell you, it would be much easier if I could switch Windows from one language to the other on-the-fly !
I don't think MS is going to come up with that feature any soon, but I've already done it and would love AwareIM to enable that feature ... when most other features have come true.