Honest question, outside of writing your own bot are there any real IRC integrations for even half of the services Slack integrates with? It's really useful to set up monitoring services in a dev channel where we can not only read errors, but share code snippets with pretty formatting, Github integration to let us know when a PR has been opened to fix the issue, and then Trello to manage features too.
Not to mention the integrations outside of developers. I haven't worked in enough large companies, and never as a nontechnical employee so I'm not sure what sales teams were using for communication but I doubt IRC was their cup of tea. I imagine they used a lot of email, maybe some CRM communication but that's still not as useful, or rather I imagine it's less useful than Slack. Having a single place to discuss Stripe purchases, hiring with Breezy, MailChimp et cetera that isn't a gigantic email forward sounds seriously useful and I don't know that anything like that exists on IRC.
There are alternatives like HipChat, but they clearly didn't it the mark the way Slack has.
You make a good point about all the integrations. I might be in an minority situation, but none of the people who are enamoured with Slack that I work with are using any of that stuff. It's just instant messaging with a sprinkle of file sharing to them. It seems to me the biggest thing, as others have pointed out, is the polish and the native apps. For example, Hangouts does most of it, but Google has killed of their native apps and the in-browser experience is really suboptimal. Having a simple, dedicated, well designed native app really makes a difference.
Not to mention the integrations outside of developers. I haven't worked in enough large companies, and never as a nontechnical employee so I'm not sure what sales teams were using for communication but I doubt IRC was their cup of tea. I imagine they used a lot of email, maybe some CRM communication but that's still not as useful, or rather I imagine it's less useful than Slack. Having a single place to discuss Stripe purchases, hiring with Breezy, MailChimp et cetera that isn't a gigantic email forward sounds seriously useful and I don't know that anything like that exists on IRC.
There are alternatives like HipChat, but they clearly didn't it the mark the way Slack has.