Re: anyone had any experience with Zulip?
We have installed Zulip internally and have been using it for about 6 months or so. Personally I like it a lot. The way streams and topics work. Pretty much everybody in our tech team is now using it, even the grumbling oldschoolers who saw it as another toy.
It was also super easy to integrate Nagios alerts and git commits into it.
Unfortunately, the Zulip iphone client sucks - but the desktop and web clients work nicely. Installing the server is not quite simple but once done, it seems to Just Work. All in all, I'm quite pleased with Zulip being an alternative to modern hip chat clients but having everything in-house and not liable to some bullshit TOS like Slack has.