I downloaded Google Talk a few days ago. It seems that is the only IM client that can penetrate these dark and ominous firewalls here at my company.
It works great, so far. It doesn’t, of course, integrate with any other protocol, so you’re sort of limited to the gmail user base; but it’s neat and simple and does what it’s supposed to do.
One feature that strikes me as odd: You can decide to let Google Talk set your “away” message to the mp3 song you’re currently playing. I wonder who thought that feature up.
You are not limited to GMail users! Out in the free world, outside Redmond, people are standarizing the IM universes around XMPP (aka “Jabber” – why did they give up that name for yet another boring acronym?). Google Talk is built around XMPP and you can add Google as a federated network in your organizations Jabber server.
XMPP does not yet standarize voice and video communication, but there is a lot of work going on and Google says they will support the standard.
There are also gateways between the open world of Jabber and the darker corners of the world called MSN, AIM and ICQ.
Read about it here: http://www.google.com/talk/developer.html and federation is announced here: http://googleblog.blogspot.com/2006/01/open-federation-for-google-talk.html