You said it yourself. The Django ORM is designed for relational databases. Django-nonrel seems to work, but it's a second-class citizen in the Django world. Much of the appeal of Django resides in the ecosystem of pluggable apps, and most of them won't work or will fail subtly when running on GAE.

Okay, fair point about the third party apps. But even without them, it's not obvious to me that writing a Django-nonrel app from scratch is the worst option available.

Django is a full-stack framework with a monolithic approach. The fact that it is possible to switch some of the components doesn't really mean that it is advisable to do so.

I've worked with Django for 3 years, and in my opinion Django actually has a non-negligible learning curve. If you have to give up the benefits of the full-stack approach and of the Django ecosystem of pluggable apps, you might as well go with something simpler, such as Bottle or Flask, or choose a full-stack framework that officially supports GAE, such as web2py.

I've tried django-nonrel as well - if you're not trying to get an existing django app running on app engine, I'd stay away from it. In practical experience, we saw our handlers taking 3-5 times longer when using Django-nonrel.