At my current job, you would have to pry Slack from my cold, dead hands. I would rather deal with conference calls on personal cell phones than go back to e.g. Chime that Amazon used. For me, it's not just about communication (although there are 1,000 ways that Slack reduces friction), it's also about the searchable archives. It's the equivalent of Stack Overflow for our internal issues.
That's funny because there's a stack overflow for business and it was passed over for slack.
Another thing is -- the public stack overflow is really nice for reference, but in my experience I don't like the culture around it. It isn't inclusive. The thing that turned me off was when they would shut down a question because it would lead to extended discussion.
Now slack allows extended discussion - properly off in a thread - and through that fosters a corporate culture in a good way.
