The video below shows how Windows Phone 7 devices will connect to Zune PC software and some of the features this partnership has. "Zune software is the only way to transfer music, movies, photos and podcasts from a computer to a Windows Phone (without using the cloud). To transfer any of the files to a WP7 device the file can either be dragged down to the phone icon in the bottom left of the screen or by right clicking on the item and selecting "sync to [device name]". In the video the wireless sync functionality doesn't appear to be working, but this'll be working when the devices are launched. Zune software will also be used to update WinP7 devices when there're large updates to download and install."
Zune v4.7 will be required to sync a WP7 device with a PC, and has a few other minor improvements (other than support for Windows Phone 7) including better navigation options for browsing photos.