Running Pure Django Projects on Google App Engine
code.google.com
code.google.com
General Django PaaS will probably be 'nicer' with the various less-restricted options that are springing up (be that mine, ep.io, or others, like djangy, gondor.io, apphosted, or the several others I forget), since those tend to lessen up on the "it must scale" aspect and focus more on making the 99% majority of sites (i.e. medium sized or smaller) work well.
Overall, I am very very happy with Django on GAE and develop with it, even though I've developed with Flask as well. With microframeworks I generally find that you need to reinvent many of the things that Django already provides.
Your only objection that I can see is really the fact that the ORM joins, so don't. As long as you keep that in mind, everything else is transparent because it's really the same as what other hosts offer (memcache, email, tasks, etc).