Here in Southern Arizona, there were very few traffic updates, so I set a destination for Phoenix and had lots of information. Clearly, Navigon is not always sourcing information from smaller U.S. cities.
As a comparison, I tried the traffic info built into my car nav system, and it displayed 9 nearby traffic incidents, some as close as 4 miles away. At the same time, the nearest traffic incident I got from Navigon was 94 miles away in the Phoenix metro area.
It was odd, because both systems source a lot of the same places (like Clear Channel Radio) for information. On the other hand, the traffic info from Navigon was more detailed, with nice close-up maps of the trouble areas.
I like everything about the Navigon app. The graphics are first rate. It automatically changes to night view, the text to speech voice is very clear in a noisy car, and the map doesn't lag from my actual position.
The traffic option is US$19.99 as a one time payment, and not overpriced in my view. My only caution is you may not get much information if you are not in the large metro areas, and it would be nice if Navigon posted where good traffic information is available.
For those in the bigger cities, it's a nice addition at a reasonable price.