Please let this put an end to the hipchat/slack madness.
Hipchat/Slack bring a lot more to the plate than just text chat, I think there is room for a customized IRC system to fill that gap, but it would take a lot, including native apps, notifications and tight control over granular settings, as well as centralized permissions for larger teams.
Inline images are annoying and I don't like that it uses non-standard protocols.
I also understand that Hipchat is not open source completely, and if so I don't like that.
Notifications are part of a client.
Permissions for large teams are nice, that is a useful feature I would like.