"Familiar", eh? To me it's still "that weird new hipchat competitor people keep talking about", but it's still something operating at a couple of degrees' remove: I've never used it or met anyone who uses it or heard of any reason to use it, and the one time I went to the website it wasn't clear that there was any way for random people to sign up for it. I'm curious why you see it as the established standard - isn't it basically brand new?

Slack built up $11m in annual revenue in a really short time, and is adding $1m in contracts every 11 days. At what's about $7/person/month, that's a lot more than no one.

http://www.businessinsider.com/slack-growth-after-one-year-2...

Maybe I'm just old and cranky, but to me both Slack and Hipchat are IRC knockoffs.