Sonos has built a flash version of its music controller for online demos. It's neat, and was probably worth the investment it took to build because the UI (depicted below) is a key part of the Sonos value proposition.
However, one of the more interesting pieces of feedback I received from my Sonos review was from people who wanted to know why Sonos was worth a price premium over simply sticking an iPod and a speaker dock in each room.
There are good answers to that question, but the experience is different, and that doesn't come across in an answer - or a demo of the UI. The controller isn't the experience. Having easily controlled music throughout your home is the experience, and, that may take an actual physical demonstration at someone's home to generate the a-ha! moment Sonos needs.