I think they're great. When I returned the leased BMW X5 last summer, the 'inspector' said that the cars with the sensors were always less 'dinged'. I back out on to a sidewalk from a narrow garage. I can't see squat. I walk out and look both ways before I back out with emergency lights flashing. I listen to the PDC carefully. Pulling into the garage, the lights and sounds enable me to get 8" from the right side cabinets and 8" from the work bench on the right front everytime (even after a refreshing malt beverage). Not to mention the occasional pedestrian, bycyclist, etc. that perversely walks in front or behind your moving car. Then there's the idiot that leaves you 8" to get out of a parallel parking stall. With an old pickup (or a Range Rover) I could get out by 'touch' and 'spatial enlargement'. I'd rather not with the Cayenne.