I've switched over to using mattermost, it can be (and is) self hosted so I'm not as worried about slack getting hacked (again) and leaking our info/taking control of our systems with chatops.
The downside is; mattermost is not a strong replacement. I wrote a bot to basically do a large part of my job for me, and coding against mattermosts websocket protocol and dealing with authentication has been messy to say the least.
Slack is a joy to code against and use from a UI perspective when compared. (sadly, as I don't like it for ideological reasons)