What must-have/killer features won't work with IRC/XMPP gateways? Also, even if there is something, shouldn't it be optional then? I don't mind them wanting to

What must-have/killer features won't work with IRC/XMPP gateways? Also, even if there is something, shouldn't it be optional then? I don't mind them wanting to discontinue support for it, it's their business after all. I mind the BS reason. Feels like a Google Reader scenario...