The "300" Workout has grown dramatically due to it's mainstream movie's name sake. Similar to the 100 Rep workout; the 300 Workout is a test of will and very challenging. The great thing with these workouts is that they are so different from the standard heavy weight low rep approach.
There is NEVER only one way to work out.
Your body is a marvel in adaptation; it will grow to meet new challenges, then level out. The body's goal is to adapt to the work load so as that it can complete it's tasks efficiently; that's why you get stonger when you workout. By changing your workouts your body too must change to meet it's new challenges.
Muscle confusion really is the way. Now let's confuse some muscle! "Ready your breakfast and eat hearty, for tonight we dine in Hell!"