GWT sucessfully solves these disadvantages and does the "lion's share" of work.
But unfortunately the standard (or core) GWT library provides just basic functionlity and not very good range of visual components (widgets). Sure GWT team kept in mind that community will have to develop additional widgets to fill the lacks in rich UI functionality.
One of such extentions is the Advanced GWT Components library - the set of widgets providing additional features not covered by the standard GWT package. The core and most important widgets are powerful grids but the library also contains other useful and interesting tools.