Yikes. Like the upcoming Mozilla Firefox 3, this application just looks killer on Windows Vista. Which raises an interesting point: How come the best-looking Vista apps aren't coming from Microsoft? From the Yahoo! Messenger blog:

It’s here! It’s really here! We’re thrilled to bring you the preview version of Yahoo! Messenger for Vista, the first Yahoo! Messenger built from the ground up for the Windows Vista operating system. This is your chance to try it out and give us your feedback to help make the next version even better.

This is a preview version only (pre-beta) so not everything is in here that you might be used to seeing in other versions of Yahoo! Messenger. [It includes an] entirely new interface that harnesses the power of WPF, the graphics subsystem in Windows Vista.

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