Have you ever thought about using Head-mounted Displays to provide working instructions in industrial environments? Have you ever tried to perform a user based evaluation of immersive 3D technologies? Have you ever tried to setup an Augmented Reality systems of high quality? This book tells you the story of the need to work with more than 100 people to develop a mature Augmented Reality system for navigating people to the right place in a warehouse. On the one hand it gives insides in how to provide an ergonomic and usable navigation. On the other hand it shows the way, how we can efficiently evaluate and improve complex user interfaces.