We took a long-ish drive into northern Ontario and I wanted to ensure that we had decent map coverage on our phones even when we were out of a coverage area (which was fairly often on some of the back roads).
The TomTom iPhone app – only $39 for the Canada/Alaska version – worked tremendously. I found that it would naturally route us using major highways, but if we wanted to skirt through a particular town, that was easy to do.
The GPS on the iPhone 4 worked perfectly, and all turns and notifications were spot-on. The fast app switching of iOS 4 meant that we didn’t lose notifications when my wife wanted to change the music coming over bluetooth (which worked perfectly, as well).
The only thing I can think of that would be swell is the ability to route the audio through the headset profile for bluetooth instead of the A2DP so that you can still get notifications when the car’s audio was switch to the radio or CD instead of bluetooth audio.