Solid German build quality, superbly beautiful paint quality, reliable transportation, BMW expert service, decent fuel mileage, incredible sunroof opening which is the largest I have ever had, very comfortable and heated seats with (in my case the necessary) lumbar support, a wonderful stereo with rich low tones and crystal clear high tones, rich light wood accents and my wifes favorite feature, a heated steering wheel. This winter, we had to go to northern Ohio to pick up our son from college and despite sub zero temperatures, massive snow and seemingly impassable roads, the X3 handled it all like a genuine off road 4 wheeler in spite of all its sophisticated amenities!
The dealership where I bought it, They have a hand car wash on Saturdays for the cost of a tip to the car washer. This dealership makes ownership of an otherwise great car even more special! As long as they are there, I'll own a BMW...
Better gas mileage. The gas mileage for the X3 is good and especially compared to my Land Rover Discovery I traded. I would assume the engineers are working on it and mileage will improve in future years.