But, the meat of Wave isn't XMPP, its the combination of Operational Transforms on a federated XMPP layer with a web interface. Each of these features is equally important, so don't overlook them. OT makes collaboration easy, the web interface is the easiest user experience, and XMPP lets you scale the backend.
This is why I hate XMPP. Over-engineered to the point of absurdity.