I might be remembering incorrectly, but wasn't the launch option for App Engine their home-grown version of web.py?

Can you give some examples of how that is the case? I don't know of any App Engine Services available on Java not available on Python (or vice-versa). They seem to be equally supported.

It's Go & PHP that are in "Experimental" mode. (per https://developers.google.com/appengine/)