BMW engineers like to avoid accessories that are a drag on engine power, so electric cooling fans area no-brainer.
For the 2007+ model they moved to an electric water pump.
Not sure where they are with electric power steering across the current model range.
Transfer cases are thought to be a weak point with the X3 based on discussion in this forum.
Mostly it's the separate actuator that wears out, but some owners have had bigger problems either as a consequence of that, or lubrication issues.
For part of the 2004 model year X3 transfer cases were filled with A/T fluid as the newly-developed xDrive fluid was not available then.
Dealers did not replace the fluid unless a wear value code was thrown based on monitoring of resistance in clutch plate operation.
Fluid costs about $50 so any cautious owner should have had it done regardless.