We replaced my wife's 2000 528i with this beauty. I could not say enough good things about X3. If you are worried about gas mileage, or expecting soft Buick like ride then BMW is not for you. BMW is The Ultimate Driving Machine not a sofa.
Free maintenance, reliability, styling, performance, heated steering wheel, panoramic moonroof, BMW Assist, and all the rest that puts a smile on my wife's face when she's driving it.
This X3 is a sharp car and drives like a 3 series sedan...this is a blast to drive. Outside of that, it gets less attractive. It isn't very big for an SUV (ie Doesn't carry a lot of stuff or people). The fuel economy for a V6 is horrible (maybe 17-18MPG?) Four passengers in this thing feels like too many. The trunk is tiny (can't fit 1 set of golf clubs across). And the interior features aren't stellar for a $40K vehicle.
Exterior looks, fun to drive.
Upgrade the interior. Make it just 6-12 inches wider.
The 2.5 has been surprisingly zippy to drive. It is the best car on snow that I have ever owned. Very rough ride and poor fuel economy are my two key complaints. I've never had any significant problems and I have about 45,000 miles on it now. It had several nuisance problems while under warranty like rattles and problems with warning lights but nothing significant. BMW seems a little loose on their quality control, especially for the price. Overall, however, the car is excellent. I have noticed it is a head turner too. People still stop and look at it in parking lots and it is two years old.
Vehicle looks, roomy interior and brakes. It will stop on a dime and give you nine cents change.
BMW X3 is the best SUV design on the road as attested to by the many copies springing up these days. The exterior alone sold me. Perfect size, perfect space, more car than truck-like, very open interior, very solid feel and very sporty. If you want to keep some of your youth but want room to haul a growing family, this is your SUV. One suggestion though: get the premium package (leather). The standard (non-premium) package feels like driving in a big styrofoam cup that's always rubbing you the wrong way and the sport package will likely make you sick on long drives. My major complaint is the price, esp. when compared with similar SUVs (Volvo XC90) that offer more.
Sharp exterior, few if any blindspots, solid feel, panoramic roof, spacious but not a behemoth, decent interior storage spots.
Better gas mileage, better interior materials (compare X3 w/ premium package to a Volvo XC90 and you'll be bummed), bigger and more cupholders, bigger glove box, stronger engine (3.0 is barely adequate), standard auxiliary input for iPod or standard multi-CD changer, lower price.