ACA maps are great if you're on an ACA route. Even there, I like to supplement them with state highway maps from a tourist information center when entering a new state. IMHO they are the best tool for the job, for the reasons given previously.
In addition, the roads I like to ride on the most are the low-traffic back roads, the ones that disappear on electronic maps (google, Garmin, etc.) when I get to a scale that I can see where they go. It is pretty aggravating to need to get somewhere at the end of a long day's ride and find out the road you've been traveling for the last half hour is a dead end.