I too have known quite a few people that have gone on various diets and kept the weight off.
I think the key to any maintaining is still exersize and potion control.
If you go back to eating junk on any diet you will gain.For me thinking i will never be able to have fruit again is just not posible.Once i get down to my goal weight I can treat myself anytime as long as i maintain exersize and don't over do the foods.

Look what Richard Simmons has done for people