Here are some Grail applet demos that have been coded to resemble some well-known Java applet demos. Notice how the Python source is usually much shorter (and consequently more readable) than the Java source.
Obviously, you'll have to follow the links to the Java widgets with a Java-capable browser to see the Java version of the widget in action; however you can follow the link from there to the Java source, to compare it to the Python source.
Performance of the Grail versions of some widgets is less than that of the Java widgets. Hey, give us a break -- so far, we've spent less than half a person year in total on developing Grail!