my mom has a 2007 x3 3.0i.
there was a little quirk once where the transmission went into limp mode. powered it off. turned it back on and nothing happened since. the motor had a loud ticking at one point also where it needed a part in the motor replaced, pretty costly i think. something like a hydraulic valve controller or something. usually happens when the car is on for short drives often. also might have been an issue since the dealership we got it from over filled the oil by 2-3 litres.
but otherwise it's been great.
2004 Silver Gray M3
Mods: Dice Unit, EAS Angel Eyes, Painted Reflectors, CSL Diffuser, Smoked Corners, PSS10s, 15mm Front and 10mm Rear Spacers.