I have found that when I use a GPS navigation device, it is only a secondary reference that I rarely look directly at. I also disable all audio output.

I find them very useful for navigating through an unfamiliar area, but I mostly see the screen in my peripheral vision because I'm paying more attention to the road and signs, etc. I can see when a turn is coming up because the brightly colored line indicating my path on the screen bends, and I complete the turn having never looked directly at the device. I do look at it occasionally when going straight to have a sense of the next road name, distance until next turn, etc.

Try this if you haven't already, because I found looking at the device too often was disorienting (especially in traffic circles or complex intersections) because the display lags slightly behind your actual position.

You are absolutely right about situational awareness though. That's always top priority and any device that interferes with it should be disabled or repositioned in your field of vision.