I'd love to try TomTom on my S3 because their iPhone app is the best thing out there here in SE Asia. The other day my NDrive quite literally led me to a sand path in the middle of some Thai mountains before it admitted that it actually didnt have a clue where my destination was. Took a 50 kilometer detour cause of that poc. My wife's iPhone TomTom had to solve the problem.
Google Nav is unreliable for us because of the often very weak data signal in my neck of the woods.