Monday Microsoft officially released Messenger 8 for Mac. The software has been available as a beta release since March.
Messenger 8 offers audio and video calls to other Messenger users, and also links in with Live ID, Microsoft's online single sign-on system. Live ID is used for MSN Messenger, Hotmail, and other Microsoft services. Probably the biggest features seems to be compatibility with Windows Live Messenger 2009, allowing Macs to participate with Windows users in chats.
Messenger for Mac 8 requires the discussed Live ID account, a 1.83 GHz Intel-based Mac or faster, and Mac OS X 10.5 or later.