I have had severe acne my entire life, and went on Accutane twice. It worked for about 6 months each time and then my acne and greasiness came back. The problem, it turns out, is that I have hormonal acne, and Accutane does not work for this.
Accutane may work for individuals who have a different kind of acne, but for me, all it did was make me severely itchy, give me constant bloody noses, and make my skin so fragile that i have scars from places where I got just a scratch. Really, it was just a mess. Have your hormone levels checked before you go on this! This is something dermatalogists won't tell you.