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Debugging is performed using "hosted" mode where the UI is constructed on-the-fly in the vm and pushed to an embedded tomcat server, allowing you to debug directly in the java code. This is somewhat useful while in development, except that the UI output is not quite the same in hosted mode as it is when it is compiled to javascript. Debugging a deployed application would be very difficult as the javascript code is minimized optimized to reduce transfer time.
Documentation
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Development is in Java, which is familiar, but tends to require a lot of code to do simple things like implement action handlers and provide callbacks. Since Java provides many capabilities that javascript does not, only parts of the standard Java libraries are supported, meaning that care must be taken to not use classes/methods/types/etc which are not supported. There significant limitations on using The ability to use external libraries is limited.
Styling is done via a combination of external CSS and embedded component styles.
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Java code is compiled to Javascript using XML config files. Along with the Javascript are HTML and CSS files (which can be edited directly) which create . All of these together comprise the application which can be served from any standard web server.
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Being able to work in Java in a manner resembling Swing is familiarnice, but it also reminds me how long it takes to create even a simple UI. Learning how to use all of the GWT-specific classes (and learning which standard Java classes and libraries to not use) would take time similar to that of learning how to use components in an XML syntax. Not being able to access REST or SOAP interfaces directly without being on the same host/port is a major drawback.
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