From 0 to $1B – Slack's Founder Shares Their Launch Strategy
I like Slack, because I can rely on non-technical people to use it, but if I'm working with people who actually know what they're doing, I don't see the advantage over IRC.For free, it's a great service.  For $5/mo it's a great service...but for $5/mo/user, it's pretty pricey!If you don't pay, it doesn't make a good replacement for email, because you don't get infinite scrollback.