The Firebase API is pretty quick after the initial connection, here's an un-optimised React version (i.e. no shouldComponentUpdate hooks) which uses the Firebase API, for comparison: http://insin.github.io/react-hn
This is pretty cool, thanks for sharing. I may start using this to browse HN all the time, since it does have the one feature that I miss from the normal site, e.g. highlighting new comments since the last time I viewed a thread. It also appears to autoload new items? I assume this must be cookie/session based, but I'll have to look at it.