To have our own Private SEO community to help us get our questions answered, Priceless..
The community is super helpful, you can ask there any question, and there's always someone to respond and help you out, about the Slack part, it's a bit annoying as a new user, but you get used to it pretty fast.
SEO guidelines changes very quickly. What worked one day not only stops to work the other day but can severely hurt your business if you continue the tactics that Google bans.
I recently learned of this and am definitely going to share it with my friends online who are bloggers and marketers!