The P21 headset is the latest PS3 headset from Turtle Beach, which replaces the now obsolete PX1. Turtle Beach has been supporting the Xbox 360 for a while with similar headsets, so it's nice to see that they love the PS3 as well.
The P21 is a wired headset, and uses a 16ft cable which is comprised of 2 audio cables and a USB/power jack. You are supplied with an USB extension in order to connect the headset to your PS3. The audio cables need to be connected directly to your TV (and/or PS3) so that you can hear the audio, and the USB connection provides power and acts as a microphone input. I'll admit that this isn't the most ideal way of connecting a headset to your PS3, in fact I'd love it if the headset was completely wireless, but the wire is long enough to compensate for this. After connecting the headset, enable the microphone audio through Settings -> Accessory Settings -> Audio Device Settings.
The main feature that differentiates this headset from other similar headsets on the market is that you can hear the game audio, chat audio and control each aspect of the sound independently, whilst your TV is muted. This allows you to play a game online (or offline), without disturbing anyone else with your gaming, as well as eliminating chat echo. Due to this feature, your chat will get through to other players crystal clear, and you can even mute your microphone at any time.