Two unique Navigon features are lifetime free map updates and an awesome highway interchange mode that makes it easy to determine which lane you should be in. It also has an excellent three-dimensional "reality view" which is extremely intuitive.
This unit pretty much does everything that I would want a GPS to do. Some more points of interest would be nice, but at this price point, I really can't complain! Highly recommended if you are in the market for a GPS unit for your car.
Update: Oops, my bad. Turns out the Navigon doesn't have free map updates after all. It does have free software updates, but probably most of the other GPS manufacturers offer that also.