With a limited selection of A2DP (Bluetooth stereo music) supporting devices, the S9 is a good value in it's class. When it does work, it sounds good. When it doesn't, it can be frustrating.Does it work? Yes, most of the time. However, be prepared for dropouts, especially in city usage. The S9 is susceptible to interference from a variety of radio sources. I suspect the bandwidth required for hi-fi music means that you'll need a better signal to noise ratio. When walking about New York City, I frequently get dropouts from my music and podcasts, particularly in intersections where I know there to be communications equipment. At home, the microwave oven will kill reception. Now this is with my Walkman phone in my chest pocket, not 10 or even 5 feet way.Sound quality: It's pretty good, but it's hard to tell when the fit is not so tight. Unlike my iPod in-ear earbuds, you can't get a tight fit, and thus you can't get a deep bass response or filter out external noise. No complaints, but I'm not looking for audiophile quality for my walks about town.Telephone call quality: Sounds OK, but no where as clear as A2DP sound. The person on the other end of the call will notice that you're on a headset since the sound will sound a bit more distant. Background noise is definitely present. Also, I find the volume balance between calls and A2DP is not automatically adjusted. One may be loud where the other is soft.Comfort: This is hard to say. I can wear them for an hour without too much discomfort. They press my temples above my ears a little, but that's just my head. They're not adjustable, so try before you buy.Charging: I hate charging another device, but as devices go, this is reasonable since it charges with a USB connection. It is a little finicky, as it doesn't like my Blackberry USB charger (possible too high voltage) but otherwise I can charge it anywhere with a computer and a little cable.Using two phones: The wife has a Walkman phone as well. When we hand off the S9, we need to re-enter the 0000 security code. I don't know if it's a quirk of the S9, or the Walkman phone.Overall: Good. If you hate wires and can accept a few dropouts, then try this on for size. In a noisy RF and audio environment, it's not so pleasant.