After having used Navigon for a few years I found myself in Europe and tried iGo. I find the navigation information display superior to Navigon - iGo is quite intuitive. I even purchased the US version.
The downside, and its a big one, is the keypad as iGo does not use the native iOS keypad so it is not calibrated or have the native feel. The keys feel cramped and are more error prone and the typing experience feels slow. A navigation app does not need to complicate typing.
Cayossarian about North America - iGO primo app, v2.3.2