Ron - I've installed the OEM front and rear camera's to several X5's. The rear camera sticks out like a sore thumb. One of my business partners had his stolen while parked in NYC. What we use is a discrete camera mounted in the centre of the rear Roundel. It's so much more low profile than the OEM unit.
However, the front OEM camera is brilliant. People often ask what the point is but the beauty is that the monitor splits the screen showing you left and right at the same time. This is very useful when pulling out of driveways or blind intersections.