They had a pretty good presentation at Boulder Java User's Group yesterday about Vaadin framework.
Vaadin uses GWT. I played around with GWT a long time ago but it always struck me as sort of a crutch for the JFC/Swing developer transitioning to web development, and these days it's not like there's a lot of those. But the code in the demo app seemed pretty reasonable. I didn't pick up on the GWT connection until someone mentioned it in the Q&A so it wasn't a big distraction or anything.
The presenter Marcus Hellberg worked through this example in about half an hour giving a sense of how easy to use and powerful this framework is. It was nice to see someone using Spring in one of these presentations and it is cool that Vaadin is available right there in the Spring Boot Initializr. The demo app demonstrated some low-key dynamic effects like making DOM elements appear and disappear.