While I can see the advantages of document databases in some use cases and I can't help but feel that a lot of adoption of MongoDB and its ilk are more related to the rough edges of interfaces/ORMS to relational databases and not fundamental flaws in the relational databases them themselves. This coupled with fact the rising generation of developers is less familiar with SQL than the last is leading to some curious choices for datastores. It should be an interesting next couple of years.

Also great work on Alembic, I started using it a few weeks ago and am very pleased.