Finally, I don't have to run Yahoo for those few friends who insist on using it. You can chat with Yahoo friends through Windows Live Messenger (fancy name for the new version), by simply adding them as you normally add a contact with their full id, such as email@example.com or firstname.lastname@example.org.
However to make it confusing, the below message appears on Windows Live Messenger, making you believe that you have the wrong version. Just ignore.
More on MSN Messenger's Blog, click here
Update: 1 day after I tried this it's not working everywhere. Some of my friends in India on the Yahoo side aren't receiving "add" requests. So I guess we'll have to wait a while....wonder if this will cause the idea to bomb?