The emissions control system for the North American diesel X5 seems to have been a slight sore spot, dogged by SES lights and various recalls and campaigns. Given that this was the first time BMW tried out the urea injection, perhaps not much of a surprise there. The same drivetrain X5 3.0sd has been sold for awhile outside the US but didn't need the urea injection to meet CARB standards, so BMW worked around that to make it compliant. But with workarounds, there tends to be a higher risk of unforeseen issues that require updates and the occasional recall.
The rest of the issues seem to be centred around the electrical systems, on which the vehicle is very dependent. These vehicles are intended to be driven, so BMWs that don't see a lot of driving or highway stretches tend to be unable to maintain sufficient charge, and then a whole host of gremlins can crop up.
My dad's 2010 X5 has been less than reliable, between the build quality (abnormal wind noises, rattles, squeaks) and the two issues mentioned above. He plugs it in to charge the battery every weekend, similar to a plug-in hybrid.
Last edited by AzNMpower32; 01-01-2013 at 10:10 AM.