We're still doing it, though not as extreme as we were at first...but enough for us to both maintain our weight loss.
I think it taught us to steer away from so much processed empty carbs and eat more veggies and high fiber carbs. Totally turned my IBS around and I've not been bothered with it for almost a year and half.
Steve lost 45 pounds and I lost 15. And we've kept it off easily.
This is the crux of the plan. The problem is too many folks refuse to read the book and follow it as it was written. The restrictive part was only for two weeks and then you gradually added in the carbs to where you stopped losing weight and then cut back 5g a day until you reached your goal weight.