I've been using Slack in my classes for a year, now, and the response from students has been overwhelmingly positive. So much so that when my students then take classes with other faculty who don't use Slack, they're confused as to why not.
In this EdSurge article, Amy Ahearn, senior innovation associate at Acumen, discusses how to use Slack for workshop and training purposes. By using channels as breakout rooms with returns to a main channel every 15-or-so minutes, it seemed to work wonderfully:
The result? People from a range of backgrounds joined the real-time conversation, including a high school student in Seattle, a UX designer from Sydney, a front-end developer from Indonesia, an activist from Virginia and a professor working on MOOCs at Cornell. We had four active Slack rooms and 22 people dynamically contributing—an admittedly small sample size in the world of online learning, but instructive for a prototype.
The conversations were able to get deep and complex quickly and the platform enabled the +Acumen team to dip in and out of conversations in a way we can’t do in our traditional MOOCs. “Very fast moving. Amazing to see such wisdom and deep discussions shared,” one participant observed. “In a very small amount of time, we touched on a lot of key and very insightful points,” another added.
It's encouraging to see innovative uses of technologies like Slack that are ostensibly aimed at team communication.