I didn't buy an iPhone until the 3GS, but I never used turn-by-turn navigation. I just needed a map with directions that I could refer to if I got lost. After I got it, I also discovered how useful it was for planning trips by bus. Did the original iPhone not have Maps at all? I think it would have been a killer app even without turn-by-turn.

Well, people don’t carry a Garmin when they ride buses I guess? iPhone’s navigation didn’t become reliable enough to replace a Garmin / Tomtom till 2011-2012.