with an apple tv, you can download music from the central music server (mac with itunes) the just use front row to view the selections with cover art. you don't even need the touch or iphone. just use the little remote that comes with the device. the other benefit by doing this is you get a multi source setup which you can play different music than from the central music server. or you can just pipe the itunes from the mac thru the apple tv.
iphone/itouch 2.0 software release
with the introduction of the new iphone along with the 2.0 software release for both the touch and iphone, you can download a program for free from itunes that allows these 2 devices to remote control a central itunes on a mac for a whole house audio setup. it gives you the capability to use the same GUI of itunes to pick your songs along with selecting which apple tv or airport express device you want to use. if you were thinking about getting remote buddy or another piece of software to control your itunes on a mac, check this software out. so far, it works flawless. there are hundreds of other apps that you can now download to use on these devices.