I have an inexpensive Garmin for navigation (made certain to get a model with full North American map database plus almost all of Europe so it can be easily moved from my vehicle to a rental car when needed.)
Really posting to tout an app called Waze. I have the free version on my iPhone and iPad. It provides decent point to point navigation but the real value comes from user based highway reports and the easy ability to IM other "Wazers" that are displayed as avatars on the map. People who use it are very helpful. It does require operation by a passenger, however. Would not be safe to try to use it while operating a vehicle.
Technical demands for loading and efficient use are very manageable.