Being able to setup your own server is a benefit, not a negative. Much like twitter it seems to be another regressions from an open internet to corporate control.
The only positive I can see is rich text, but that has extremely limited value in a chat program. History is nice too but IME too painful to use (scroll, load, scroll, load, scroll, load) to be of any practical benefit.
Slack has search for history, which is huge. No more "eh we talked about it".
Onprem is great. But it's a hindrance for quick adoption.
I'd love if an open system would win. I've no love for Slack and don't use it. (Have used hipchat; what a UI mess like all of their products.) But I guess no one stepped up with an IRC-based platform that could compete.
For functionality like that it sounds like a mailing list would fit the use case better.
> Onprem is great. But it's a hindrance for quick adoption.
It's not either/or. Think of git, you can use a hosted server or a private one. The ability to host your own server doesn't hinder anyone.
Then you're looking at an email with the visual noise of recipients and whitespace and signatures, and if the UI is really bad (mailing list websites, for example), every message is viewed in isolation without the responses.
In short: Slack is what you get when you have a team managing an IRC server with all the nice plugins and bots and building a single UI that does everything. You can spend your time setting up the same thing, or you can go to Slack.
Why not make IRC easier to setup?
* offline messages * full history access and search * fancy authentication schemes
There are some who try to build a full experience similar to what Slack is proposing; I'm thinking of IRCCloud for instance. But then instead of being stuck inside Slack, you're stuck inside IRCCloud (note: for the nice features, not for the basic messages). What we'd need is an open source IRCCloud server and client, that would then become the new standard... then only can IRC compete.
So, it's not just a software issue, it's a protocol issue. Which is why XMPP was born, and Matrix was born, and all other IM protocols were born. But none of them has reached the point where they can overwhelm all the other ones combined, so in the meantime people converge towards a centralized system because it's easier to be up-to-date.
A webbased irc client that doesn't suck (and keeps a channel log) would probably be a good solution to making things easy for people unfamiliar with IRC.
Some sort of one click setup for a channel on Freenode or a similar network would probably be pretty popular - especially if you could get some useful bots from the get go (like git ones) .