Thanks to this BBC NEWS | Technology | Google sets tongues wagging with Talk I've just realised that Google Talk is based on Jabber. This means that we will eventually see it working with other protocols (and that I should be able to get it to work in Miranda IM).
But IM is still way to geeky. Until anyone can talk to anyone, like the phone or email, then it ain't going to work for most people I know in 'real life'. Then we can just on with choosing which client we like, just the same as we can choose our email client or mobile phone.