I've had
Navigon MobileNavigator with the Live Traffic add-on for a few months now.
I have a windshield mount and the Kensington Liquidaux (charging, audio out and remote control) so the iPhone audio goes through my car stereo w/line in. Still working on a clean install and resolving ground loop issues.
Made a mount for the remote, not sure I'll stick with it.
Last weekend driving from NJ to NY was like a scene out of a commercial: I queued up my news podcasts in a playlist, hit play, loaded up Navigon, selected the "Audio book" option for iphone control which automatically pauses audio during announcements (vs the music option which slightly mutes it.) It had me going through the Lincoln Tunnel, 20 minutes into the trip I hear "There are new traffic notices for your route." Click the traffic icon, it shows an alternate route over the GWB will save 20 minutes, select it, it recalculates, shows I'll be home at 8:20. I hold down the home button for voice control, say "Call home", it dials, hit speakerphone, "I should be home around 8:20", end call, navigation resumes, podcast resumes. Pretty sweet.