The album art and titles pop up on your aTV screen much like they do when your running iTunes with the visualizer full screen. That is, in the bottom left hand corner. It streams from you computer library to aTV, it treats the aTV like any other airport express, which is what I have going on in my family/living room.
Unfortunately, it doesn't seem to be able to group multiple speakers with my airport extreme. In otherwords, my computer+aTV= OK. my computer+aTV+BOSE [the name of my airport extreme]= NO GO. It says it can't combine/do you want to switch to BOSE. I'm expecting this not to apply to multiple aTVs.