Macworld seems to think they are the best two nav apps available for the iPhone. I am very satisfied with my Tom Tom app and GPS boosting cradle and the traffic rerouting has saved my butt a few times. But I am jealous of how frequent and substantial the updates are for the Navigon app. Comparison reviews here:
I've been thinking about buying this app for a while, and now it just went on sale. The reviews on iTunes are about 1/2 and 1/2, but the negative ones are much less credible. Any opinions?