AirTunes is renamed to AirPlay, and adds video and photos. It's still a push setup that will also allow pushing that content off an iOS 4.1 device to the Apple TV. And yes, iTunes 10 sees my AirPort Express and Apple TV first gen as valid AirPlay targets, for audio only currently.

Apple is also working with 3rd party device manufacturers to add AirPlay to their devices, like speakers and such.