Hi forest faerie, I did somersizing to lose the first 75 lbs. Loved it, loved it, loved it, it helped me break a lot of bad habits and start eating whole, healthy foods. Nothing to count, eat til I was full (then quit) and a wide range of foods, you just have to watch how you eat them. After about 75 lbs and 6 months, I wanted to add a few things to my foods. Things like pb, oatmeal with butter, the occasional sweet potato with my meal. I started tweaking my plan somewhat, then became curious how many calories I was eating, and started counting calories. Along the way, I've turned more to calorie counting, while still eating what would be considered level 2 somersizing.
I agree that the food you can eat is awesome. You don't have to buy anything special (I have never bought any of her products). She has some great recipes in her books.
I was only eating about 4 - 5 carbs meals a week, usually in the morning (loads of veggies with the protein meals), and I did experience some problem with constipation in the beginning. I started drinking psyllium husks in water to help that. That was about the only downside to the food plan
Edited to say that I lost much quicker the first 6 months than I have at any other time. It's difficult to say if that was due to the diet or due to the fact that you lose quicker when you are so heavy than you do as you get smaller. Several times I have been tempted to go back to level one to test it, but I enjoy my oatmeal with Smart Balance spread and my peanut butter sandwiches too much to try it.