Google App Engine is free, so the app is live for you to take a look. http://udnotes.appspot.com/
To create a GWT application mainly 3 parts would be hard to understand for new users:
- Create a client side code. This is all about simple GUI app implementation. Instead of using Swing Component, you use Component from GWT.
- Communicate to Server with RPC. Here is the part required more attention.
- User Google DataStore data. The cool part is here.