I bought this Bluetooth Plantronics 510 in June of 2006.Why I bought it:Price was less than the competition for comparable bluetooth units.The shape puts the weight behind the ear.The discreet, understated boom on the face; long but not too long.The built-in rechargeable battery.Why I like it:It worked with my Sony Ericsson Z520 as adverstised.The weight was well balanced and it feels like it will stay on.It is very comfortable. I hardly notice it is there after a few minutes.The battery has never given out on me. It has good standby power as well as talk power.The on/off button is simple and logical.The volume up/down is easy to get to, and there is good range in volume. The volume is sufficient for car travel and I have never had any complaints about the quality of my voice on the other end.The receive call and hang up button on the unit works as it is meant to. If it is pressed twice in quick succession it will call back the last number dialed.The phone rings with a call coming in, and the Plantronics unit has a clear beep. One press of a button and I am hands free, talking.I can use it on either ear with a simple adjustment.There is a little wind noise if you are outside and it is breazy. I don't think that would be unusual for a mic exposed to the wind. I don't expect it to perform well in the wind so I don't count it against it.Sometimes a person just finds the right thing that works well. This is one of them for me. Thanks to Amazon I got it at a great price too. I highly recommend it.