Me too. I've tested my GPS in places that I know the best route, and some times the GPS, while it will get you to your destination, will go round about, and many times only that it can get you to a toll road.
I semi-trust my GPS, but if you have it set to use toll roads, it can really take you out of the best route.
Just FYI, its not GPS that routes you to the wrong place, its Garmin or whoever implements the map software. GPS by itself is very reliable.