My Devoxx takeaway this year is definitely without a doubt AngularJS! It is an awesome client-side MVC framework. It is what HTML would have been, had it been built for dynamic content. It has two way data binding, it supports templates and dependency injection, hell, they even designed it with testability in mind. If I were to build a new web app, I would use AngularJS on the client side talking JSON with a RESTful Spring app on the server side!