Google Maps is great for a few tens of miles, but for anything longer, I'd get an actual map, for sure.

I followed the Adventure Cycling Northern Tier maps last summer. On the outskirts of Muscatine, IA I lost the next map -- the one going across IL and IN. I didn't realize it until I made it downtown, several miles of unpleasant riding into a headwind later. Oddly, I had a decent idea of where I lost the map -- the last place I had stopped because I pulled it out to plan where to stay that night, although I certainly wasn't sure (otherwise I would have picked it at the time... duh!).

Anyway, I couldn't bear the thought of going back at first. That day was, literally, the low point of my entire tour both physically and mentally. I figured I'd just get lunch in Muscatine and then plan a route across IL and IN in the public library using Google Maps and, perhaps, a gazatteer. It became clear pretty quickly that it wasn't a reasonable way to go.

Purchasing maps from a gas station along the way likely would have been okay, but I was so discouraged by the thought of planning a few hundred miles worth of riding this way that I turned back and, miraculously, found my map.

It actually ended up being a good evening, and I wrote about it in my journal here. (Hint: it was my one night in a hotel for the entire tour.)