iGo primo has decent graphics, including both 2D and 3D navigation displays. My iPhone 4S had no problem getting and retaining a decent GPS signal in testing and my onscreen location was very accurate, generally matching my actual geographic position.
There is a free, maps-only "lite" version of iGo primo that lets you search for points of interest near you. The full app, which I looked at, provides unlimited navigation including an on-board map.
Using text-to-language technology, iGo primo correctly pronounces city, street, and highway names as it guides you to your destination. It can also read out a summary of the planned route, traffic events, and relevant country info after crossing a national border. Choose from seven different languages: English, French, German, Italian, Spanish, Portuguese, and Russian.
Another standout feature is its realistic junction view capability, which provides true-to-life images of motorway junctions. This is a huge boon, especially if you're making the "great American road trip" and driving places you've never been. Knowing exactly what the exit you're supposed to take looks like can be a big deal.
One of iGo primo's other advantages is its optional Live Traffic add-on software. Live Traffic lets you see road congestion and traffic jam information in real time, and iGo primo automatically generates alternative routes based on this up-to-date info. You don't have to lift a finger. In addition to North America (an extra $37.99), Live Traffic is available for Europe, Italy, France, Scandinavia, Benelux, Brazil, and Russia.