Yeah there are boring stretches. In the desert on a long straight road where you can see to the horizon...nothing but pavement and dirt. It can get boring. But like others have said, the boredom rarely lasts long.
To be honest, since getting out of the army, getting a corporate job and having a kid and all the busyness that entails, I now relish boredom...having the time and mental emptiness to just be alone with my thoughts is a luxury I don't often get these days. Some bike rides I pick the most boring route just to get that.