I have used most of them including Hipchat and for some reason Slack seems to be the best, with full features, like hubot, sharing documents, links, private and

I have used most of them including Hipchat and for some reason Slack seems to be the best, with full features, like hubot, sharing documents, links, private and custom chats etc. This project looks like it is going in a similar direction and could really compliment Dropbox and compete with Google Docs. Just as long as they don't make you agree that all stored data is theirs to keep (yes Google does this now).