My connection always sounded great with my 3gs. Both my 550 and X5 were great. Then I got the iPhone 4! Since then everyone tells me it sounds like I'm talking on the phone with all the windows open. My iPhone had this problem with 4.0.1 and after recently updating to 4.1 the problem persists. I called my home voice mail from my X5 bluetooth and when listening back it sounded pretty bad. At this point I've narrowed it down to the iPhone 4 since my 3GS and my wifes blackberry sound fine in my X5.