Really? I wondered what all the hype about Slack was.
So, Slack is basically Colloquy, but for Windows morons and Linux weenies.
That's depressing.
They have a way better client than hangouts for OSX, about the same on android.
IRC is like USENET: It has barely evolved for decades, nobody can profit by improving the protocol as it's a commons, so it just stagnates and dies out.
Eventually all the decentralised protocols that were born in the early days of the internet will be gone.
This means that server-side innovations can and do happen - they just need to respect the basic server-client protocol. Often the newer features are delivered through "services", which means they're in-band signalled.
Also, Slack bought a company which did voice, video, and screen sharing. Since join.me went downhill, this will be a welcome addition to Slack.