Zune is sort of the substitute for Windows Mobile Device Center for Windows Phone 7. And although it wont sync, files, contacts, calendar, it is the new way for you to get multimedia files onto your WP7.
But not only can you add music, photos and video files from your PC, you can also buy them from Zune using a Zune Pass.
Plus you will be able to browse and install the games and apps Marketplace, and install them directly to your device.
To see more check out the following video: