I purchased this because I had a good experience with its predecessor (the 655) but I hated wearing an earpiece while in the car.  The Discovery 665 has a wonderful car charger/holder that allows you to dock the headset conveniently in the charger until a call arrives - at that point you simply pull the 665 out of the charger and it connects the call as you are swiftly inserting the headset into your ear.  It also seems to perform better in screening out wind noise than the 655.  After the call is ended just hang up by removing the 665 from your ear and inserting it into the car charger/holder.  This is a big improvement over the 655 and suits my purposes (not wearing a headset until a call arrives) very well.