The key to successful gps use is to plot out the route in advance using pc software, verify the route clearances using at least two sources, look at any portions of the route you're concerned about using google earth and then transfer that preplanned route to the gps. The gps then becomes a scrolling map that can warn of hazards and tells you where to turn.
If you simply plug in a destination you'll be one of the thousands who complain that the gps "led me the wrong way" etc. No map database can have _all_ road conditions and hazards correctly listed.
