Here's another React version which also does comments (and allows you to fold them - I needed to write a userscript for that before!). It's using react-router to switch between top stories, comments, individual comment and user profile pages.
http://insin.github.io/react-hn
I've just gone for it with Firebase's React mixin, binding everything as an object, since their devs in this thread don't seem concerned about rate limiting. The mixin seems to throw an error every time I try to unbind, which I'm just catching and logging for now.
Edit: I just watched this comment pop up live in my version - pretty neat :)