I've been toying a bit with Google App Engine. I was lucky enough to score one of the 10,000 developer accounts. I first went through their tutorial, which was fine. Then I tried to port a simple application that I used to run from the command line, which queried a range of IP addresses for their reverse DNS names. No luck. I was using the dnspython module, which in turn uses the Python socket module -- and socket is not available within the Google App Engine sandbox environment.
Also, I was talking to Michał on rewriting the Cheesecake service to run on Google App Engine, but he pointed out that cron jobs are not allowed, so that won't work either... It seems that with everything I've tried with GAE I've run into a wall so far. I know it's a 'paradigm change' for Web development, but still, I can't help wishing I had my favorite Python modules to play with.
What has your experience been with GAE so far? I know Kumar wrote a cool PyPI mirror in GAE, but I haven't seen many other 'real life' applications mentioned on Planet Python.