It's nice to do a tech talk again, instead of always doing a keynote about the future of Plone. Sorry, I can't show you details, because I got laid off and there is a non disclosure agreement.
SQLAlchemy allows you to talk to SQL databases in a Pythonic way, getting Python objects as results.
Martijn Faassen created Traject, combining routing and traversal. Izhar Firdaus wrote collective.trajectory to do this in Plone. We use this to traverse to SQLAlchemy objects, by registering functions. We hooked the results up to plone.app.contentlisting as well, so they show up correctly in listings, like the standard tabular view.
A trajectory example project: https://github.com/esteele/example.trajectory It has add and edit forms which talk to the SQL database.
We had really a lot of tabular data, so it made sense to do this in SQL, not in a normal Plone portal type.