I read about it recently and it doesnt sound healthy at all. Sounds very much like the atkins diet to me and limiting carbs from your diet completely can really affect you health. i always feel negative towards low carb diets as my aunt who was relatively healthy apart from wanting to lose a few pounds had a massive heart attack while on a low carb diet.
Carbs are healthy if you eat the right ones, i.e. wholegrains etc.
It is easy to lose lots of weight with those kind of diets, but maintaining it is where the problem lies.
my friend also does it and has gotten a good weight loss but it seems very restrictive. Apparently you cant even have fruit because of the carb/sugar content? It does seem quite complicated but there is a dukan forum on minimins where they explain things (went on there once for advice on cooking for my friend).