I successfully did the program losing over 30kg and maintaining the weight loss for almost a year now.
For me it was an easy diet to follow as most of the allowed foods were what I would crave for on other plans (dairy, steak etc) and I've never had a hard time giving up sugars and flour before. I had to adda lot in the way of fresh vegetables to my diet in order to keep with the alternating days. The idea of eating to my natural hunger levels also appealed. No limits on amounts worked well for me and saw my eating fall to natural levels early on.
Others find it hard and it is in many ways restrictive and for some there may be difficulties. But the high protein, low carb option which Dukan represents was a match for my specific needs at the time.
Tips. If you have any hunger or cravings while doing the program .. Eat!
The allowed list is the allowed list! Simple!
Understand the process by which this diet works (ketosis) which is s recommendation for any diet someone starts. Don't do it just because it worked for someone else. Do it because the foods appeal to you and it makes sense to you. Or you won't stick to it.
Explore the recipes out there for using the oat bran. It keeps the side effects of the diet at bay (regular fibre)
Have supportive people around you.
There is a dukan thread on 3FC, though it is very slow, but there are active forums around for support if you want.
Follow the rules, but remember that while off plan will slow you from achieving your goals, it's not the end of the world. Just get back on plan as soon as you can. Guilt equals eating for many of us.
Eat! This diet really works best if you eat when you feel hungry and stop when you don't. It has that freedom for you and it helps keep the feelings of being deprived at bay.
Results will vary, but it did work well for me and repave me the chance to change my relationship with food to something much more natural and intuitive, I am fit and active (do the walking, it is enough on it's own while losing weight. You can do more if you want but it doesn't make a big difference)
check your bloods with a GP, as you lose weight, your body will release stored cholesterol (any diet that causes fat loss will do the same, including low fat diets) and this needs to be monitored. It should drop back to normal after you maintain your lowered weight for about 4-6 weeks.
I hope it works for you as well it has for me.