Built from the ground up specifically for Microsoft Windows Vista, this all-new version combines the reliable and easy-to-use features you’ve always loved from Yahoo! Messenger with the cutting-edge experience of this new operating system.

• Instant message, voice, webcam video, and more
• Use the integrated Yahoo! Messenger Sidebar gadget to keep up with the friends that matter most
• Also add Windows Live™ Messenger friends to your contact list to see when they’re online and IM them
• Keep conversations organized by dragging and dropping them into one tabbed window
• Brand new emoticons, program icons and alert sounds
• Instantly change the look and feel of your Yahoo! Messenger interface
• Automatic groups are created in your contact list based on your Yahoo! interests (i.e. Yahoo! Sports Fantasy Football league)

Heres a cool video of how it works straight from Yahoo Labs!

http://messenger.yahoo.com/vista_popup.php