+1 on avoiding the first year or so of production.

Consider that the 2004 was a significant refresh, with a new engine in the 4.4 model, new transmissions with more gears, and new x-drive. More features, and more to potentially go wrong. Some purchasers go for the 2004 up to get better mileage in the 4.4 models.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue