This is really great work, guys. We've been using Firebase for a while now. The uptime, low-latency, and consistency have been impressive. A good security framework was really our last hurdle. We're digging in to the new security features and pretty happy so far. Another good resource (in addition to the blogpost above) is the quick start page. [1]
Also, one side note: it's not always clear from reading the docs, but changes to the security rules can be made dynamically and take immediate effect.