To clarify my point about the Volvo and BMW AWD experiences, I really didn't have a chance to push the X3 in a way that demonstrated its capabilities. When I drove the XC60 however, I parked with the passenger side in sand/gravel and the driver's side on semi-wet pavement. Then, I put the accelerator through the floor and experienced almost no wheel spin. Within 20-30 yards, I was able to effortlessly merge onto pavement without having to let up and did so with full traction.
Admittedly, this isn't the best way to test either vehicle but when you're on city streets and you've got the sales guy in the back seat, you're bet to keep the lid on.
Maybe there's a better way?