It is simple behavior modification, you stop using a skill and you begin to lose, becoming more and more dependent on the technology. It does actually change your brain over time. The exercise of using your brain on the navigation skills, along with memory and being more aware as you travel, keeps the brain healthier and more able to learn. Dependency on such things as GPS (as useful as they may be) means you do become less able to learn over time.

Morals to the story, exercise your brain, and skills trump equipment every time.