Although it's good, the system is still no match for a human navigator. The computer will never say: "Turn left at the Dog and Duck" or "Go under the iron bridge". Destinations have to be entered in the zones the computer understands. The system doesn't cater for postcodes although a postcode facility is being planned for the next release.
The computer stores the names of roads, the screen shows the name of the road you are on and the one you are about to turn into, but the system doesn't read them out. This is a shame, as the reassurance would be welcome. The weakest aspect of the system is that it calculates the shortest route, not the quickest, and the computer takes no account of traffic flow. This is fine in a Porsche at 3am, but in heavy traffic, when overtaking is difficult, a link to a traffic database would be a distinct advantage.