During the early stages of training, instrument familiarization is one of the best uses for PC flight simulators. With the advent of multi-core processors and powerful 3D graphics cards, the interior of an airplane cockpit can now be reproduced down to the tiniest detail. In fact, some of them actually have better graphics than full motion airliner simulators. The first few flight lessons tend to be extremely intense, and students rarely have much time to study the instruments closely. The simulator gives the student an opportunity to spend some time alone in the cockpit, and learn to recognize which instruments are which and how they work.
Altitude familiarization is another very helpful skill that students can reinforce with the simulator. This involves using the view out the window to determine the aircraft's position relative to the ground. While this may sound like common sense, in reality it takes time for new pilots to do this on an instinctual basis.
Finally, the simulator is extremely useful for students learning to fly properly in the traffic pattern of an airport. Once more, it takes practice to recognize the proper sight picture for flying a downwind leg, or knowing at what point to turn base and final.