People I call when driving with the top down tell me they can plainly hear road noise, wind noise, trucks passing me, and such. Tried with the Mot BT HS850, and with just the Treo hand held; no difference. Before I had a Mot V60 and with no headset most people were surprised I was in the car; it did very well.
I've given up on BT, plan to add Voice Dailer, but need a recommended headset, BT or wired, whichever works, that cuts out the background noise.
Mike