I use screen protectors on phones/mobile devices, as the screens do tend to take a beating. The protectors do reduce the glare, but they also reduce the clarity of the screen somewhat. Next, unless you’re experienced at putting the things on, then you will have air bubbles. If you have a problem with decals, you'll have a problem with these things. I'm willing to put up with the protectors on phones/mobile devices, as it will be better in the long run; once you get some scratches then it's hard to read the screen. So losing a little clarity on the beginning is worth it. On a NAV though, I don't see the need.