NAVIGON North America [$89.99 - iTunes link], just let us know that, fresh off adding text-to-speech for street names, they'll soon be adding real-time speed information from actual drivers on the road, traffic messages, road sensors and cameras, and historic traffic flow data to reroute iPhone users around problem areas.
MobileNavigator North America [$69.99 - iTunes link], by Navigon, is the second GPS TBT app I examined. This one requires you to download all the maps in advance (1.5 GB for the US version, 1.67 for the European version) so make sure you have space on your iPhone. The advantage of this is that you can get GPS directions even if you do not have an AT&T signal. In addition, the actual “routing” process seems a little faster since it is not downloading directions OTA.