You can't join multiple groups/teams with HipChat, which is one of the most absurd design assumptions I've encountered. This was completely unusable for us, and

You can't join multiple groups/teams with HipChat, which is one of the most absurd design assumptions I've encountered. This was completely unusable for us, and many others. For reference, have a look at their uservoice thread, which has been running for a few years and has a few thousand votes