Regarding the debugging features, I think things have gotten a lot better. Debugging is done in Eclipse and you're debugging java, not javascript (if that wasn't clear to some). It honestly works really well. I think there are also quite a few benefits other than type-safety. Easy implementation of asynchronous calls that serialize Java objects is one example.

GWT does have its drawbacks, but we do a lot of complex work in it with very minimal native javascript and support a site with hundreds of thousands of active users.