I’ve been using the beta version for a while now and have found it to be quite useful as it incorporates several features all in a convenient "Sidebar". For example, the default settings gives the ability to search and index your Gmail account, display your Google Talk contact list, and display a list of popular web news based on your past surfing preferences. Of course, the latter will only be shown if you give Google Desktop the power to monitor your surfing habits.
For more information, head over to the Google Desktop Download site.