Just a way better interface on it. Searchable history, multiple rooms inside rooms effectively. File sharing, lots of niceties that are probably possible in IRC but would take a lot of work. It has changed the way our team communicates, for me I am the only remote guy on a team of 6ish devs. I can pick and choose my hours, work when other guys are off, and still see all the comms that happened while I wasn't at my machine.
Right. Think of Slack as a really well configured IRC server, except you don't have to manage it at all, and it's front-end UI is much more modern (and better); integrated file uploading, inline media, integrations with everything under the sun, etc. None of it is impossible in IRC, it's just _easier_ in Slack because it's out of the box like that.
And, most importantly: I don't have to manage the damned server ;)
There are a couple of protocols that do similar things, but nearly all of them have a major fatal flaw, that is unfortunately very difficult to work around through no fault of their own: mobile push notifications, especially on iOS. An open protocol is useful, but not enough, and that's where Slack hosting and developing everything themselves has an advantage, despite open protocols and tools being what I'd normally want to use. But practicality matters, and so when I last looked at alternatives a year ago, I couldn't find anything that would be a drop-in feature-complete replacement. It's a shame, but I expect something to come up in the future, perhaps on Matrix or other protocols.
True, and I use a bouncer myself, but it's something you have to set up explicitly - Slack already does it for you. Notifications as well - you can get emails, or texts, or the app on your phone can ping you.
And sure, a bouncer with some plugins could do it, but you'd have to set it all up. I've had "have bouncer email me when I'm mentioned in a channel" as a mental to-do for the past five years, and it's never been a high-enough priority for me to sit down and expend the minimum of two hours it would take (and likely much more.)
I love everything about Slack except the damn chat window. Oh, and the pricing. The onboarding process is buttery smooth, and there are tons of integrations. But there's so little in the way of communication density (even in 'compact mode') that I miss IRC.
We have a jira integration set up and every ticket consumes five lines plus plenty of whitespace - a few of those and there's no real comms visible on the page. Every integration I've see consumes gobs of space. Similarly, flagging announcements by assigning a colour is almost worthless - the colour bar isn't very visible (I prefer hipchat's method, where the entire chatline gets the background colour set). Then there's the problem of people's actual chat messages being the least visible thing on the page - smaller and less noticable than names, integration notifications, what have you. But the onboarding is so easy, it just sucks users up.
Being able to see a conversation instead of bells and whistles? I miss that... but plain text scares regular users...
I hear those complaints, we found them early on too. We have since separated operational noise in to other channels that ONLY contain integration related stuff, and try to keep one channel purely for actual chatter.
