The flying skill level is not that much more. Handling the complicated systems and flying well can be. Most jets have to use flaps, brakes and retracts. If you are not comfortable with these systems you better be before attempting to fly a jet. Otherwise it could be a very expensive endeavor. Now add twice the speed of flying and most landings and you get the picture.

Moreover, like others have said, it is complicated just starting them and making sure everything is proper. All in all it is a much more complicated system to operate and control.