1.) It's not a 'diet'. It's really based around solid principles of eating - eat frequently, balance your meals properly with the right foods and proper proportions of protein, good carbohydrate, and good fat, eat lots of vegetables and some fruits, limit refined carbohydrate consumption, don't eat too many calories at once, etc. So it teaches good eating habits that are sustainable for the long term.
2.) Other times when I have reduced my calorie intake to drop bodyfat, I end up with horrible cravings after about two days. With the Zone Diet, I didn't experience any of these. This could be for a variety of reasons that Dr. Sears discusses in the book.
3.) The block system for keeping track of portion size is very easy. After about a week of weighing and measuring your food, you can easily keep track of the exact amount of food you need in a day. And this works whether at home or eating out.
I've also gotten great results using these principles with clients of mine time and time again. If you want to know more, do yourself a favor and pick up a copy of the book!
The Zone: A Dietary Road Map to Lose Weight Permanently : Reset Your Genetic Code : Prevent Disease : Achieve Maximum Physical Performance