If you have interacted with the GoGrid web portal, then you have seen our implementation of GWT. It helped us provide an extremely rich experience of server-side code while preserving the speed of client-side code. The end result has been our award-winning interface (winner of LinuxWorld 2008 Best of Show).
The Google Code group interviewed Justin Kitagawa, Technical Product Manager and lead on the GoGrid project about his usage of GWT within the GoGrid framework. Below is the full video, which even shows some of our new GoGrid features.
The video can also be viewed on the Google Code Developer Videos section of their site.