I've been building https://github.com/mattfeldman/nullchat, a meteor chat application as part of a commit-a-day pledge of working with meteor.

I think the reason there are a few of these popping up is that it's a lot of fun to build a chat application with meteor. I never intended to be a 'clone' of slack as as much as rocketchat or spacetalk.

I've been running it for a small group (~10 active daily users) for about 6 months - it has more social features like rich embeds, mentions, notifications, sms gateway, giphy search etc.

Demo Instance: http://nullchat.space