Uber was on Hipchat, briefly experimented with Slack, went back to Hipchat, and then moved to our own Inhouse chat based on open source project, starting around the beginning the year.

It was bad the first few months, but except for a recently publicized utterly embarrassing security vulnerability, in the last 2 months it's been working great. The mobile app is now much, much better than the HipChat ever was.