I love having a phone and mount on my bike. I use it for GPS mostly. I bluetooth music and GPS directions right into my helmet with a Sena attached, and yes I can talk on the phone if I want to. I can even make phone calls hands free. I don't talk on the phone to gab, but its nice to have for emergencies and long rides.
I've only got experience with a couple of different phone mounts, but make sure whatever clamps your phone to the mount doesn't interfere with the buttons on your phone. I had one mount that was hard to get my iPhone mounted securely without pushing in the two buttons on the left side of the phone.