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.