[zak_mc_kracken]

irc supports pretty much nothing besides text. With Slack, you can format, highlight code, upload pictures and documents, it supports Google Docs out of the box, there are plugins for Trello, git, and who knows what else. And it works flawlessly on all mobile OS (good luck getting a decent irc client running on iOS).

irc is a dinosaur compared to what recent team communication software like Slack and Hipchat can do.

[mikekchar]

Although I don't necessarily disagree with you, none of these things are particularly difficult to implement. In fact, most of it could be done very easily if you had a client that could render/inject markdown. Git and trello bots are very easy to write -- almost kata level scope. Famous last words, but surely this is not hard given that there are 3rd party libraries for everything you need... I'm almost tempted...