Clojurians Log v2

The other (big) thing to consider is admin functionality / moderation -- Slack is very well-designed for that since it's meant to support companies and therefore has, on a per-team basis, full support for owner / admin / member hierarchy with permissions and the ability to manage rooms (and people!). Most of the other options being touted as alternatives to Slack don't have that in any reasonable form because they just sort of assume they are centrally operated (somewhere, somehow) and that any member can join any channel on any server. Given the abuse I've seen on, e.g., Mozilla's IRC servers, and a couple of other chat systems, from trolls and spammers, I'd be very leery of the very openness that many (end users) seem to want in these discussions.

And there's also the big UI/UX issue. IRC has had #clojure for years and it's a decent-sized community but the Slack community exploded and is many times larger. That seems to be true for every IRC channel I've seen that gets a corresponding Slack team: I'm in over a dozen Slacks, about half of which had a corresponding IRC channel (or set of channels) before and every single one of the Slack teams dwarfs the IRC community. People really like Slack's UI/UX and the relative ease of discoverability. None of the other options suggested come close.