Um I am a XP developer and when I used GWT I found that it hindered TDD. Their test framework was awkward as hell to integrate and it was slower then shit. 10 seconds of setup and 10 seconds of teardown is completely unacceptable. As a result we needed to create extra layers of separation to let our test suites run in a reasonable amount of time. The rails platform was developed with TDD in mind, so their tests take about 0.05 seconds for setup and teardown. When compared to a framework like rails GWT shows very clearly how it was not developed with common problems faced in mind. Take for example implementing validation, in rails it is 1 line of code in the model and 1 line of code in the view to show validation messages. Now in GWT to get this same functionality you need to implement the whole validation system tits to toes. There are so many other points to be made against GWT, no MVC structure out of the box, if you want to know how changes actually look on a page you can't trust the hosted environment. It actually behaves quite differently then ie7 once you get really deep into it. So if you want to change the position or color of a button, depending on your code base say hello to 1-10 minutes of waiting. I could continue to go on about how awful GWT is but you should just take my word for it and try Rails instead. You will be much happier.