I've owned these for over a year now and, despite being functional wireless headphones, I'm not really happy with them.
I purchased these from Amazon for £60 in August 2007 so that I might listen to my music without the hassle of wires (which I'm prone to tripping over, forgetting they are connected to me, etc.)
I sent my first set back believing them to be faulty: If I turned the volume up on my computer to the max and the volume on the headphones down low, the volume of music would become incredibly wavy (going up and down where it wasn't meant to). After a phone call to Sony I learned that they have a special volume levelling ability that basically decreases the volume of sounds deemed "too loud" by Sony for the user to bear.
This causes a couple of problems: Even with my head touching the base station whilst wearing the headphones, I get static in the background during quiet sections of songs. I cannot rectify this by turning the volume up on my computer since the volume will be instantly lowered by the base station (apparently some kind of health & safety thing so that we don't sue Sony for damaged ears.... they could at least put it in the headphones themselves and base it on the actual volume output!).
Also, there is occasionally interference picked up by these headphones when sitting a couple of feet away from the transmitter. This noise is resolved by turning your head at strange angles to get a better signal from the transmitter, it would seem.
Other than that, they've served me well since my purchase but, due to my problems, I don't really use them anymore.