[EGreg]

Wait

What exactly does Slack do that other chats don’t?

If you had to boil it down to 10 main features what is the point of this? Realtime chat seems to me to be distracting, and I much prefer threaded forums and issue trackers. But I’m willing to listen.

[haute_cuisine]

It's most likely already installed when you send an invite to someone and they already used to how it works. It just works most of the time, well, besides slightly buggy text editor and almost non-working calls.

[EGreg]

But so what, browsers are installed too and can load arbitrary websites. Which can implement all that stuff too. And threaded forums like Discourse are far better.