If you're using Glass for navigation, it generally stays out of the way. If you're approaching a turn you're due to make, it will beep at you and a voice will tell you what to do. Only at that point does the screen come on, and displays a fairly simple map drawing. Once you take the turn, the screen fades off.

If you're wearing Glass properly, the screen is also up at an angle above your eye. If you're sitting in the driver's seat of a vehicle and looking forward, the display would be about at the area where your sun visor would be if it were flipped down over the top of your windshield.