I am against the wimpy runtime assertion in Sven's patch, since assertaions may be disasbled. I think that swapping out a HandlerManager is inviting problems for developers, and I can't think of a good use case for it. If we are only going to allow one HandlerManager, it should be baked into the API.
http://gwt-code-reviews.appspot.com/138801 -- http://groups.google.com/group/Google-Web-Toolkit-Contributors
