Since late August 2010 I've been on Medifast. Going on Medifast was a pretty big deal to me because I tend to be highly skeptical of weight loss companies, particularly ones that require you to purchase their food. However, I had heard good things and it seemed to be based on relatively sound nutritional principles, so I decided to go for it.
The first 3 weeks were a bitch. I was hungry, complain-y, mentally out of it, and I had cravings. Now that I have gotten used to it, it is a lot easier. I feel a lot less hungry and if I am careful about eating every couple hours I can avoid feeling hungry almost entirely. I'm still getting used to this mysterious "not hungry/not full" feeling, which is pretty new to me.