Russ,
I had to buy a Mophie battery pack to make the iphone last the day, and I carried another separate battery pack/charger. The navigation in the city actually relied more on good old hard copy maps and addresses, with the phone just to help gauge time of travel and search for addresses. In areas of lower buildings the Garmin was much better, it was only in the urban canyons of the high rises that it had problems.