I co-maintain an open source project on GitHub that's somewhat popular (>1.5k stars). We set up Gitter because I preferred Slack which my collaborator didn't use, and he preferred Gchat which I didn't use, and Gitter looked like a reasonable middle ground. Since then it's mostly been a communication channel between us two. We do get a user question once in a while, and I do answer when I get a notification email. Basically, for users it's like opening an issue, just less formal.