Once you master GWT you can really be very productive in it, while allowing you to:
-Write statically-typed code
-Maintain large projects using packages and OOP
-Use unit testing, code generation, and refactoring tools
-Use many Java libraries out-of-the-box or with minor modifications (this part I often find mind-boggling)
-Write code that works on server and client (also mind-boggling)
-Ignore the DOM, just use widgets
-Ignore the vast majority of cross-browser issues
-Get great IDE support
-Readily deploy apps in servlet containers like GAE or Elastic Beanstalk
-Get very performant, minimized production code
-Get help implementing best practices such as safehtml
-Interleave with JavaScript
Main drawbacks are that there are few well-maintained widget libraries, compiler takes forever, Google has been a bit reluctant to expand JRE emulation, and the script format is a bit annoying. Java is also not a great asynchronous language since it lacks anonymous functions. However, if slightly uglier looking code really concerns you, you probably don't have your priorities straight.
I don't really know what the point of Dart is. I suspect it is being promoted more out of legal concerns over Oracle than out of technical merit.
I'm constantly on code reviews for and occasionally writing GWT code, and the gymnastics and ceremony it requires on top of the slow compilation are painful enough, and the resulting JavaScript/html unpredictable enough, that I would refuse to work on any new project that used it.
It's just a tool that makes your existing HTML/CSS/js knowledge useless, a crutch for java blubs.
-Write statically-typed code
-Maintain large projects using packages and OOP
-Use unit testing, code generation, and refactoring tools
-Use many Java libraries out-of-the-box or with minor modifications (this part I often find mind-boggling)
-Write code that works on server and client (also mind-boggling)
-Ignore the DOM, just use widgets
-Ignore the vast majority of cross-browser issues
-Get great IDE support
-Readily deploy apps in servlet containers like GAE or Elastic Beanstalk
-Get very performant, minimized production code
-Get help implementing best practices such as safehtml
-Interleave with JavaScript
Main drawbacks are that there are few well-maintained widget libraries, compiler takes forever, Google has been a bit reluctant to expand JRE emulation, and the script format is a bit annoying. Java is also not a great asynchronous language since it lacks anonymous functions. However, if slightly uglier looking code really concerns you, you probably don't have your priorities straight.
I don't really know what the point of Dart is. I suspect it is being promoted more out of legal concerns over Oracle than out of technical merit.