I'm also on Team 8, couldn't resist speaking up as well
Slack has been very useful to us, we make consistent use of it, some subteams more than others, but overall it's proven to be a fairly effective communication tool. We use it for group discussion, calendar updates (there's a Google Calendar integration for Slack, any updates or new events we add to our team calendar get posted to one of our teamwide channels), brainstorming, and general coordination. It really helps make sure everyone is on the same page with what we're working on. If you have any specific questions I'd be happy to answer them, but my general response is: yes, it is mostly definitely useful, would recommend.