I think it was in the Zone Diet that I read every diet works for 20% of the people and that most diets have gotten something right, just not everything. I like to read about diets, understand the theory behind them, and then incorporate the best parts into my regular diet.
One of the biggest problems I see is people treating weight loss like a project that ends. And at the end, they return to the habits that made them heavy in the first place. Just to continue with a strict diet, I like Tim Ferris' advice about having one day a week where you can cheat. You don't go crazy and pig out but if you're on a diet where you feel deprived, that's the day when you satisfy your craving.
Be sure to exercise.