@technomancy Yeah, I've been using it for several years. It's, uh, not great in a bunch of ways, and the original author seems to have abandoned it, so any time Slack pushes an update that breaks shit (frequently!), it's the time of monsters in the Github Issues for the project.
Even with the downsides, it's hugely better than the official client, because I can maintain multiple conversations at once, and I hacked up ERC-style `C-c C-SPC` rotation through any unread channels/threads.
Before I got it working, I was using Slack in Emacs via weechat + wee-slack + weechat.el. Don't really want to switch back, it was kind of a fragile setup and not as good as emacs-slack IMO.