Personally I like to use Adventure Cycling routes when there is one that goes where I want to go. They pretty much eliminate any need to route plan and I'd rather just ride without to much messing with the route. It makes it easy to look at the map and know what you options for the next couple days are at a glance. Most of the maps have elevation contours which I find very helpful. Also it is nice to know where all of the services are and on some of the routes lots of free places to stay are identified.

BTW, contrary to what some folks will tell you on most AC routes you will not be riding with hoards of other riders or riding through towns where the notion of a long bike tour is completely old hat. Even on the Trans America we typically met other riders only occasionally. Some days we might see a few and some times we would see none for a few days. We often met locals who lived right on the route who had no idea that they did or what we were doing.

I do typically second guess the maps and take a different route for some portion of the trip though.