Well my buddies don't seem to have problems of that sort.....I saw the usefulness of the device ... thats why I got myself a unit.
Actually it does not work the same as the amb... it uses infrared transmiter on board the car and the the device is placed at the point where the car slows down to pick up the signal.
The only problem where signals not get picked up is that you tint your cars winscreen.
..... it is not working on radio signal like the amb but infrared....signal don't go through the tinted screen. It is written in the manual. One more thing is that the onboard signal transmitter ..you'll need to place it high enough to the clear windscreen (side ones) for the signal to pass through. I hope this info helps.