Mat Schaffer pointed to this library earlier, and I experimented with it a while back for a personal project, building a desktop version of the Myers Briggs Temperament Sorter (I need to dig up the source code). The Thinlet library made it ridiculously easy to wire in a nice looking GUI to my app so I was able to concentrate on the quiz logic. I’d use it in projects if I was doing lightweight desktop Java applications.
I’m looking forward to Mat’s X-Plat strategy to take hold.