Well, I do not have much spare time to take a deep look at all the new technologies that come around but i always try to check at least the minimum.
Google App Engine offers a nice tutorial : http://code.google.com/appengine/docs/java/gettingstarted/
I did not run into any major problem.
The result is a very basic and classic guestbook application.
Building and uploading the web application from Eclipse to the App Engine is a piece of cake. You must first receive a code on your phone in order to create an application ID :
You can see it here : http://celfertest.appspot.com/
I am looking forward for more fun with GAE in the near future, when I have the time.