It completely worked for me. I lost about 40 pounds on the diet a couple of years ago, and have just went back on it. For me it is great because snacking throughout the day is what really gets me. I dont snack at all on this diet.
To be honest i dont do the whole 1/3 thing at the reward meal and i still lose weight. My only issue is that I am young, therefore i go out and drink and it sucks because it is breaking the diet. But i limit those nights so they don't make too much of an impact.