I'm using web2py for a small web app. It's running the HITs on a Mechanical Turk project, and giving me an interface to control and visualize them. I started on Google App Engine, but then got sick of the little annoyances of not having direct database access and having to wait forever each time I want to upload my code, and moved to a local server with postgres. GAE makes most things harder in order to make a few scaling things easier... stay away from it unless you really need their scaling help.
I like web2py a lot. Compared to Django and Ruby on Rails, it's WAY easier to learn and get going. Everything is simple. You get stuff done fast. Massimo is everywhere solving your problems (even on this board haha).
