The diesel engine is truly the best everyday engine for this SUV. If you are test driving one of these, put the transmission in "DS" and 6th gear at about 40 mph and hit the throttle! The torque moves this vehicle with authority that the gas (non x5M) engines just cannot muster. I managed 27.9 mpg on a 175 mile trip which beats a coworker's Lexus RX400 hybrid and the x5 is much more engaging to drive than the RX. I may be in the minority, but I think the diesel engine sound is pretty cool and I dig the sound when accelerating with the windows down. You will turn some heads in parking lots when they hear that growl and turbo spool up.
I like the fact that it is assembled in the USA even if it has a high number of imported parts. As a result, it only takes about 4-5 weeks to order one. The "Top View" camera system is real nice and beneficial. The diesel engine's power and economy. The Nav and heads up display unit work well.
BMW's option prices are a bit ridiculous and should be lowered or placed into more value oriented packages. It would be nice to see lane departure or blind spot monitors added as standard features.