I suspect most people in the "Slack is a just a pretty IRC," are discounting the non-text-messaging features. Beyond both the items already mentioned and the ea

I suspect most people in the "Slack is a just a pretty IRC," are discounting the non-text-messaging features. Beyond both the items already mentioned and the ease of adoption, the major benefit to slack is the integration ecosystem. SlackOps is a really big thing. Making slack the glue across variety of operational systems to coordinate the activity of a team and allowing that team to communicate about it, provides a ton of value. And importantly, allowing this to happen organically with non-IT staff creating their own workflows (in the way that people invent alls sorts of min-apps in spreadsheets) is pretty powerful.