GWT may have been an impressive solution for a problem that existed when supporting legacy browsers such as Internet Explorer 6 was still an issue, but its time has passed.

The general idea was that you get the mature tooling and strong typing of Java, and abstract away all the browser nastiness. Best of both worlds right?

The problem with GWT is that you are only using the Java language, and so you are missing all the libraries that make Java such a rich ecosystem when run in the JVM. The abstraction layer it forms keeps your developers locked in a world that is neither Java, nor modern HTML5/ECMAScript. So instead of learning to use new browser features, your team is stuck fighting GWT's idiosyncrasies and waiting for it to finish compiling.

If you are considering frameworks for a new web application, go for Ember or Angular. GWT is obsolete and will hold you back.