I’ve been playing around with AirPlay recently, getting 3 Airport Express and one Apple TV. Since we’re an iPhone household, it made sense to use Apple products for streaming music and video. Also, you can get an Airport Express from eBay for $60 or so. Compare that to the cost of Sonos (The only real competition I’ve found out there), and it’s a no-brainer for whole-house audio and video.
Once you’ve attached (easy) and configured (easy) an Airport Express and attach it to a powered speaker or receiver and iTunes & iPhone, it’ll show up as an option in Airplay enabled apps on your iPhone/iPad/iTunes. We use it to play music to multiple speakers throughout the house and backyard and to stream video to the AppleTV. Instead of having someone look over your shoulder or give them your iPhone or iPad, simply stream it to the TV. Simple as that.
It’s good to live in the future.