If you are simply adding BT to your roadster I'd suggest you buy a good BT ear piece instead. Something like the Jawbone Icon which has great noise cancellation. On the other hand, if you have a radio that supports BT and you are simply adding on to that then I think you'll be surprised how well it works.

My Jawbone gives a better sounding signal back to the other party than the BT that I just had hooked up to my new Kenwood. However, if I use the Kenwood instead of the Jawbone it means that my radio will automatically mute when a call comes in. Also, I find it easier to talk to my passenger if I dont' have something stuffed in my ear.

As I mentioned earlier, when the installer put the Kenwood in on Saturday he mounted the BT mike on the windshield pillar. Here is a photo. It doesn't seem to pick up much road noise, even at freeway speeds with the top down.