I did it a few years ago, and lost about 50 pounds. I learned to be very picky about what food to order - if it was something that turned out well in the microwave (like a pasta dish) it was O.K. "Meat" type dished, not so much.
And I spent a lot of time working out my servings (O.K., I had two eggs, thats two protein servings, so I get one more, so tonight I'll...) and worrying about what to eat next. It all became very tedious.
BUT I did learn what 1200 calories a day looked like, what I should be eating every day in fruits and vegetables, and how to count fat and carbs along with calories. So now I'm doing it on my own, buying Lean Cuisine, remembering what NS recommended for a snack, etc.