Good plane recognition and object positioning, well-calibrated visual inertial odometry
Can have issues in poor lighting or plain backgrounds. Needs looking around first to detect flat surfaces.
We're implementing ARKit scenes into Episode 2 of our Victorian detective adventure Silent Streets: https://youtu.be/n6xY0p-IjC4
Apple's tech is two heads above the conventional simplistic AR like Vuforia (which was used in Silent Streets Episode 1).