It took less than two hours to convert Cogteeth¹ to run with the Google App Engine. Admittedly this is a pretty simple example since cogteeth doesn't use a database and Django is supplied with the App Engine environment.

All that was necessary was:

1. Create a main.py: Since the app is Django based this was just a modified copy of the version on this page.
   
2. Create an app.yaml to pass all URLs onto main.py and serve the static files directly.
3. Modify some URL fetching code that previously used urllib2 to use urlfetch.

When I say it's running with the App Engine that's not strictly true. It runs locally with the SDK, now I just have to hope they work through the wait list quickly and send me an invite...