I didn't make the decision. Slack started to appear and I didn't know that IRCCloud had apps (which seem to have great reviews). If I had known, I would have suggested it as an alternative. As it was, I just kept quiet as Slack seemed great - even better than HipChat, which I used to use for the same purpose.

Perhaps IRCCloud could be sold as a rebranded Enterprise app as an alternative to Slack? I'd love to see some competition as it looks like only HipChat and Slack are getting talked about.