I just got my 11 X5 back in Feb. I had a NOx sensor fail, which the warranty covered ($750 job at dealer), but then my EGR Cooler just cracked and the warranty company just refused it ($1600 job at dealer). I've taken the car home and am now going to replace the EGR cooler on my own.

Overall I'd say don't bother with the warranty, ESPECIALLY if you have any mechanical ability to do some fixes yourself.