So how long until Apple updates iChat to have native support, or someone builds a service plugin for it?

Any chance Messages on iOS also gets it?

Can it deliver to and maintain a consistent chat history over multiple clients? For example, a message for me should be sent to my Windows Phone, my iPad, iChat, and Xbox. I send a reply from any one of those four, and that reply should also appear on the other three. That way, if I pick up or go back to re‑read that conversation later on from anywhere, it will have a complete chat log.

This doesn’t necessarily mean that video chat works, right? You’ve still got codecs and whatnot to sort out. I don’t think Messenger works via H.264.