I just installed Google Talk (talk.google.com). Its REALLY cool.
It’s a basic IM and its in Beta but the Voice has a really good quality.
I really liked the fact that they use an open standard, the Jabber/XMPP (www.xmpp.org) which is always good. This means that you can use any Jabber/XMPP supported client like iChat (for MacOS), GAIM (For Windows and Linux), etc.
Read their developer manifesto here, to see that they mean business and I do hope that they will use the built-in federation ability of the Jabber/XMPP protocol to federate messages to other IMs such as Yahoo, AIM/ICQ and MSN.
In addition to that, it seems they are also planning to take on VoIP to standard phone which means they will take on Skype and the rest.
Having a big, money full player in this market is a good thing for everyone and even more so if they are willing to open up everything and inter-connect to the other players.
This is a great day for SIP/VoIP/IM. Mark it in your calendar.
LET THE IM REVOLUTION BEGIN!