It's an modern IRC-like experience for the web.
The primary goal is to maximize the ease of access: you can just go to
http://hackchat.net/ and start chatting.
You can also share a link directly to any channel, for example:
Pick a nickname for yourself:
You can join channels by saying
/join #channelname. If the channel doesn't exist, it will be created for you.
If you're on multiple channels, Ctrl-X will change the active one.
You can list available channels by saying
Your channels are saved in the URL so you can save it and get the same set of channels later.
That's about it! You can also leave feedback on channel
As a bonus question - if you're looking for an IRC replacement, what would be the killer feature for you?
CoffeeScript all the way. Express on the server, jQuery on the client, and socket.io in between. Stylesheets are written in LESS and served through the connect-compiler middleware. Redis is used as the session store.