@chuckd05: Fortunately, I haven't experienced any issues with Bluetooth and iPhone on the 120BT; grant it, I still use a 3GS. My mic is mounted on the driver's side pillar, too. Phone calls are crystal clear.
Which model of iPhone do you have? I know the iPhone 4 batches were peppered with issues. My wife's first 4 model had a terrible antenna; it dropped calls like crazy. We bought her a new one ~5 weeks after, and it's had no problems at all.
If I were a betting man (which I am), I would put my money on your particular iPhone's hardware as the culprit especially when the other phones work without a hitch. It could be worth your while to do a quick trip to the Apple store and ask the geek-a-zoids to reset your phone. Their method of resetting the iPhone is a little different than what we can do at home, ourselves. If it doesn't work, at least you tried, right?
