Note: in June 2015, Fujifilm released the firmware version 4.00 that adds several new features concerning the autofocus. You can read my in-depth review about it here.
In my opinion, there are two ways to evaluate the autofocus of a camera. The first is to leave everything to the camera. You point and shoot and see how the camera software/hardware behaves. The second way is to understand how the camera works to get the most out of it. This requires not only more patience and time, but also the presence of various, and sometimes difficult, conditions to truly understand what the camera’s limits are.