A service person would be using AR show him where he need to go to do his work, and what is needed to maintain that equipment. The OS will recognize and identify the computers and other hardware and show me which things need to be replaced.
Medically, an AR will map the internal systems of my patients, overlay any scans that have been done, and and determine irregularities.
When flying a plane I can look out the window and see the map of the area I am looking at. This is not much more involved that the HUD that already exists for the fighter pilots.
Walking through a forest the AR will alert me not to touch some of the plants that I may be allergic to, and show me more information when I am looking at a plant or animal.