We use Matrix (mostly via Element) at Mozilla alongside Slack. It's mainly public stuff on Matrix, and the usage pattern varies between teams: some teams are ma

We use Matrix (mostly via Element) at Mozilla alongside Slack. It's mainly public stuff on Matrix, and the usage pattern varies between teams: some teams are mainly Slack and barely pay attention to Matrix rooms, other teams (like mine) kick and scream if they're forced to use Slack for anything but internal corporate purposes. New hires in such teams tend to assume Slack initially and gradually notice that they get very slow responses on Slack, and then switch mainly over to Matrix to talk to the rest of us. It's been good to us. Note that our primary comparison point is IRC, not Slack, mainly because of our project roots of openness and widely distributed contributors. So it's a serious workplace, but an atypical one. Encryption has periodically caused problems. Leaving the company and maintaining access to your communication seems to be a bit painful. Search is not great. Threads are tolerable. Inviting outside people in works well. Abuse is vastly more manageable than it was on IRC. Performance is mostly good. Both Element Web and Element on Android are very usable. Notifications are a little wonky, but I don't rely on them much so I can't really gauge whether they're good enough if you do.