I purchased the Apple Bluetooth headset when I got my first Iphone two years ago. The volume was excellent and that made the headset excellent in a noisy environment such as ones car.
When I upgraded to the 3Gs and paired the headset, I found the volume was not adequate even in a quiet room. I repaired with the old Iphone and it's fine.
So I've waiting for Apple to find and fix this bug! My old Iphone, wife's 3G and my 3Gs all have the newest firmware version 3.0 and the volume is fine with the old iphone. I have not tested on my wife's phone.
Orignal From: Apple Bluetooth Headset and Iphone 3Gs, ...