The Google team has blogged that Gmail + chat + AIM = crazy delicious and wrote some blabla about interoperability.
Well what the GMail developers have made is not interoperability. They have simply released a web based multi-protocol chat. This really does not deserve hype, since Trillian, gaim or kopete have done that for years. One can even argue it is bad news.
With interoperability, you could be able to send an instant message from Google Talk to a friend on AIM, without opening a AIM account yourself, and without even being aware this friend is on AIM. To achieve this, AIM should be XMMP compliant, but it’s not happening today.