GWT does a really good job to bring portability across browsers, just as dojo and jquery do, however if you choose html+javascript library you still may encount

GWT does a really good job to bring portability across browsers, just as dojo and jquery do, however if you choose html+javascript library you still may encounter html/css related quirks. However GWT does not do a perfect job even across browsers, we did stumble upon an events-related bug between IE / Firefox and Chrome. But that should have been fixed by now. My take on GWT is that it is another abstraction layer and so adds complexity for most uses cases, which should not be there.