An installed hands-free kit is a lot more expensive than a headset or just holding the phone to your ear, but it's also a lot safer. No ear piece to fumble with, no batteries to worry about charging and you keep both hands on the steering wheel the whole time. I can even dial the phone handsfree, just touch a button on the dash, then say "Call home" or "Call 5-5-5-1-2-3-4"
Car kits I've had previously were specific to that model of phone, when I had to replace the phone, I had to replace the car kit, at considerable expense. This version doesn't use wires, it uses the Bluetooth wireless standard, so it will work with pretty much any phone. The only down side is it doesn't charge the phone like the cradle-type chargers did.
I still need to take my car to the shop that installed the stereo to see if they will connect it to the mute wire, then the stereo will automatically turn off the sound when I receive or place a call.