I am using GWT and EJB 3.0 now on a huge project and the performance had been awesome so far. My only gripe is that there is no great drag and drop design tool for GWT in the IDE. I’ve tried some but nothing that rocks. The choice of framework really depends on what some of the requirements are for the application. For us, the GUI had to have absolutely no screen refreshes so we are heavily using ajax calls all over the place on the front end. For this, GWT really shines.
I know this thread is kinda old. But just wanted to add that GWT really flies on Chrome browser.
Struts and tiles.