With the new build, you will be able to add and talk to your Yahoo Messenger contacts within Live Messenger. We will be on the lookout for the release and will be posting the link as soon as it is released. The signup will be available on Ideas.Live.com. This deal is the first of its kind in the instant messaging world and I certainly hope that AOL will join the fun and get AIM interoperability in WLM.
Update: The beta has been released. Sign up here.