We moved from slack to hipchat at my old job because it was cheaper. Hipchat is just a terrible product, both on iOS and in the browser. Don't even know where to begin, it was just a pain to use and every employee I talked to hated it. I'll just give a few examples:

- Unreliable notifications. Sometimes it notified you about messages sometimes it didn't, no idea why.

- You could get a push-notification about a message, then open the app and have no clue who had messaged you or in which discussion/group.

- Emojis had really unintuitive shortcuts. I remember people used to send some kind of skeleton dancing all the time, because it's shortcut was a (Y) (which is commonly some affirmative/"yes" emoji like a thumbs up).

- Also it looks horrible.