Discord looks amazing but it's marketing materials says it's aimed at gamers and compares the product to Skype, not Slack. I actually joined Reactiflux on Discord today and was pretty confused as to what I had gotten myself into and why the messages where being read aloud in a computer voice.
Hehe yeah they sure are playing the "targeting gamers" card really well. I think it's kind of obvious they're shooting for far more than that. They're competing with Slack without competing with Slack, it's very clever.
Short of video calls though, Discord is essentially a drop-in replacement to Slack. We've been using it at my company, it works so damn well. I moved to it for our open source community as well. I use Matterbridge for a three-way mirror between IRC and Gitter as well: https://github.com/42wim/matterbridge/
They're marketed towards casual users but Discord is probably the best chat and collaboration software I've used so far. I definitely prefer it to Slack for professional-type stuff.
You can use Discord any want you want. If you join some popular Discord server, odds are it'll be full of spam and Internet humor, but obviously you can do whatever like on your own server(s).
