When we reconstructed our house a few years ago, we included all kinds of wiring for top of the line centrally controlled home stereo. However, for a number of reasons we never installed anything fancy. The main show stopper (apart from price) was that I wanted my iTunes collection to be accessible, and then the only real answer is Apple. The Apple TV is a first step, but that doesn't give me access to music in the kitchen or bath room.
With the launch of the iPod Touch however, we now have an elegant streaming device with a most fancy touch screen. The disc space is not even needed, I can store all my music on my desktop Mac Mini (with 500 Gb extra disc). An iPod Touch anywhere in the house has to be connected to an amplifier (in the basement) and that amplifier is in turn connected back to speakers up in the room where the iPod Touch is. We already have wires for the speakers installed, I just need to add a cable from the earphones out to the amplifier. The music is streamed over WiFi, so if the dock looks a bit elegant this could just be the most sophisticated looking home stereo setup at an acceptable cost (if you compare it to a typical Bose multi-room system). And there's no real limit to the number of installations. Each room needs an iPod Touch (€ 299), speakers (depends on the quality you want) and an amplifier (these can be expensive).
Cool! I think I'll start with the kitchen as I can use the existing mini stereo which holds an amplifier and speakers.