I have owned trucks and SUVs all my life and I have yet to own one that is as much fun to drive as the X5. You pass other drivers like they're in reverse and it corners and brakes like a BMW should. It's one of the best looking vehicles on the road and no matter how hard you push it, it wants more. However, every other month another sensor or display light would go off or hose will leak or seal break and I'd get hit with another $500 bill (at a minimum) to fix something that just shouldn't go wrong (door locks, airbag light, etc.). It was always something. If you have the patience and another vehicle to rely on, it's a great car. If it's your only car, check your roadside assistance.
Looks, comfort, performance, features/amenities. An absolute pleasure to drive. Everything a car/truck/SUV should strive to be when running properly.
Reliability. It's just not that good at the day-to-day stuff. For the purchase price, many of the kinks should've been worked out.