Motion X GPS Drive: App Store - MotionX GPSpparently it is $1.99 now, but based upon my use of it everywhere from Las Vegas to Boston, I'd pay a great deal more. Turn by turn directions can't be beat. Audio guidance for $10/year. Automatic posting of location to email or social media (because I also ride horses in the wilderness and notify someone when I leave and return for safety sake) with offline map storage and motion detection for times when network or gps is obstructed/out of reach. Could not possibly say enough about my love of this program. Previously had a Garmin interfaced to my laptop with mapping software which was great, but this fits in my pocket, mounts on my dash, etc. Prefer Motion X GPS for riding, hiking, etc., particularly with the terrain view and detailed track recording, etc... but you asked about driving.
Waze is just simply addicting for me though as it provides real time notification from other users in the area. Both provide traffic view. I usually run both... but I'm pretty geeky. (between the two Motion X apps, I haven't used my Garmin in years).