This replaced my old headset I use with my iPhone in the car.
This fits better, it's both in your ear and light
BUT I can't stand the button interface.
You have to press and hold for 2s to start a call (using iPhone voice recognition) - but sometimes you will dial-last-number, as a bump in the road or turn of the head makes it think you've double clicked instead. What does the single short-click do? I don't know!
Worst of all is ending a call.
Is it a single click? Long press? It seems so variable! This might be in part the iPhones fault, but I've lost count of the times I've voice dialled someone, the iPhone has misheard me, and I've not been able to cancel the call.
Too often I've had to take my eyes off the road to fix the phone by hand.
This didn't happen with my old bluetooth headset.