I have been trying out the GWT designer and find it very much like developing with a event driven drag and drop style, which I find very productive. I developed a complex 10 page front end in less than a day!
I was seriously considering using GWT and the Instatiations designer in my next project. However ,I am very reluctant to proceed when all that is available is a simple HTTP servlet model that is provided with GWT and not having a better way to connect to my back end ( EJB / hibernate ) concerns me. This is not a criticism of the GWT Instantiations Designer -- it is a criticism of the GWT toolkit and a lack of forethought by the GWT designers who created the excellent GWT toolkit and didn't think that developers like me, would very much like to use it, to connect with a "back end" of an n-tier application.