You know that AIM mobile device forwarding that forwards your AIM messages to your phone via SMS? The one that just about all IM clients already have now? Apple's building a link to that feature in Leopard's iChat, under the accounts screen in preferences.
What does this do? Well, with this, you can forward your messages to your iPhone, which with the iChat-like SMS screen, gives you a kind of iChat-esque option for chat.
It's pretty ghetto, and it's pretty much the least Apple could do to get iChat onto the iPhone. How about we see a real iChat app, or better yet, a multi-client chat client like Adium?