It will be interesting to see how much succes they will have with this. They are after all up against several already established players like AOL/AIM, Microsoft/MSN and Yahoo. I hope they will get a lot of users because it will mean that Jabber will get much more use and contrary to the other IM networks, Jabber is based on the XMPP protocol which is an open standard. It is also a superior IM protocol.
The current Google Talk is missing at least a few important things though I'm certain it is only a matter of time before that will change. I'm certainly giving them the benefit of doubt :)
Update: We shouldn't forget about the Gizmo project which wqas launched a while ago as a competitor to Skype. The difference is that Gizmo is based on open standards (SIP for VOiP) and they also support Jabber so it should soon be possible to chat and talk between Gizmo and Google Talk users! That's the beauty of open standards :)