> One concrete improvement that Slack offers over IRC is that you get the history of a public channel from before you joined it in your normal client. At work,

> One concrete improvement that Slack offers over IRC is that you get the history of a public channel from before you joined it in your normal client. At work, we used to communicate via Jabber/XMPP. When we connected with our client to a group chat, the server would send the discussion history to the client, so we could see messages that were sent to the group chat even when we weren't connected. We now use Slack, and I've tried both the XMPP and IRC gateways. One thing I noticed about the XMPP gateway is that whenever I reconnected, it would repeatedly send me the last message I sent to someone or a channel. Neither gateway will replay the messages that were sent to channels while my client was not connected.