The google documentation http://code.google.com/webtoolkit/tools/gwtdesigner/wizards/gwt/uibinder_dialogbox.html shows GWT wizards in eclipse, however, on my system this is
You need to install the full version of GWT Designer. Installing the GPE only gets you a stripped down version of GWT Designer (w/o any of its wizards).
Try this:
http://code.google.com/webtoolkit/tools/download-gwtdesigner.html
Here's how I was able to get the GWT Designer tools to work on Eclipse Juno:
Not sure all the steps are required. I think the key is to have WindowBuilder installed with your GWT Designer, and remember to go to New > WindowBuilder instead of New > Google Web Toolkit