They'll slow you up. Relax and listen to the music. If your car has a tape player, bring tapes. You'll feel like you're driving in a movie. Trust me on this.
Nothing beats a two-lane road for getting a feel for the countryside.
They take you into towns, by farmhouses and roadside stands, along streams and through forests. They let you smell the trees. You smell fumes. Unless you're in a hurry or there's no sensible alternative, leave the big highways to the big trucks. If you're headed for a tourist destination during its high season, or your heart's set on a specific hotel or motel, reserve well in advance.