New icon, support for the iPad (finally), and also scaled up for the Retina Display. The iPad interface is very enjoyable. You can see your entire library, including videos and podcasts. Looks a lot like iTunes 10.
Another nice feature is support for Home Sharing. Log in with your Home Sharing credentials and you instantly see all the libraries on your Home Share. Much nicer than walking to every computer or Apple TV and dealing with PIN codes.
I can’t wait for AirPlay compatible speakers from third parties to arrive.