Slack has more speed, better integrations, better search, reliability. (For example, getting notifications on iOS.
I hate HipChat. Apologies to those that love it, but it's likely you never used both side-by-side during normal working days to compare.
So if Atlassian tried to put their mark on Trello, I have little confidence that it will still be Trello.
HipChat is certainly not perfect, but I don't agree about Slack being faster. It definitely has its issues.
Slack has more speed, better integrations, better search, reliability. (For example, getting notifications on iOS.
I hate HipChat. Apologies to those that love it, but it's likely you never used both side-by-side during normal working days to compare.
So if Atlassian tried to put their mark on Trello, I have little confidence that it will still be Trello.