I used GWT for a while in 2009-2010, and didn't like it at all. I kept running into things that weren't implemented in its subset of Java. Debugging was a pain. Compilation was excruciatingly slow because of all the variations of the code that always had to be compiled for different browsers (something like 40 seconds for a fairly small project) and development speed in general was slow. Also, IIRC you could only run your project from Eclipse in some sort of an IE6 based container. All in all, it wasn't a pleasant experience at all, and I'm not sure what the benefits are. Writing a web app in Java doesn't count as a benefit for me, especially with so many constraints around it.
Comments
I used GWT for a while in 2009-2010, and didn't like it at all. I kept running into things that weren't implemented in its subset of Java. Debugging was a pain. Compilation was excruciatingly slow because of all the variations of the code that always had to be compiled for different browsers (something like 40 seconds for a fairly small project) and development speed in general was slow. Also, IIRC you could only run your project from Eclipse in some sort of an IE6 based container. All in all, it wasn't a pleasant experience at all, and I'm not sure what the benefits are. Writing a web app in Java doesn't count as a benefit for me, especially with so many constraints around it.