RethinkDB is awesome. I have a stealth project which uses RethinkDB in the backend. I moved it over from Mongo over the weekend. It will be revealed soon. But I'm working with about 100 million records. Currently testing it with node, slamming it with thousand of concurrent requests.
Also, I just started a blog series on Rethink. http://www.realpython.com/blog/python/rethink-flask-a-simple...
Next up will be performance testing.
Congrats, RethinkDB.