It was a stated goal of GWT to produce different JS files, one per browser, so that it could generate the right JS dialect for each browser. (And so that the browser didn't have to download "if" statements containing code for other browsers that it was never going to run, meaning a smaller downloaded, also relevant then.) That always worked perfectly for me, but I only used it for about 6 months, on a small project.
Also, it had a debugging version where it actually ran the client code in a JVM, and you could step through it with Eclipse etc. Of course that didn't help if the bug only happened after the Java-to-Javascript compilation process, but in my short experience with it I never had such a bug.
Of course Javascript and the browsers have caught up, but I would have expected these features to be gladly embraced by the development community at the time, as they really did help. But they weren't.
Also, it had a debugging version where it actually ran the client code in a JVM, and you could step through it with Eclipse etc. Of course that didn't help if the bug only happened after the Java-to-Javascript compilation process, but in my short experience with it I never had such a bug.
Of course Javascript and the browsers have caught up, but I would have expected these features to be gladly embraced by the development community at the time, as they really did help. But they weren't.