I've been on it in the past (2007) and it worked great for me! My husband was so impressed with my weight loss he also started ordering their food. We are both back on the program because over the last year we simply didn't care what we ate.
Of course, our bodies are showing us the results of not caring. So, we are both back on it. I've lost almost 4 pounds in 1 week.
You eat 5 Medifast meals and you purchase your own lean and green items from the grocery. It may appear to be expensive, but when you take into account that you are no longer eating out in restaurants, driving through the fast food line, stopping at Starbucks or eating a bag of popcorn everytime you go to the movies, you realize that the cost is neutral or maybe even cheaper when ordering the Medifast meals. Also, you will no longer be shopping for 3-4 meals a day (per person) at the grocery store.
Another great advantage to Medifast is you can ask for a health coach. Health coaches are free and they will hold you accountable. You will talk with them periodically either by phone or email (whichever you prefer) and they will also give you information on support calls as well.
I've tried several of the more popular weight loss products and highly recommend Medifast. Super-easy, excellent program, lots of support online or with a health coach, and an excellent post-weight loss program designed to help you keep off your weight loss. Just don't do like my husband and I did and eat whatever you want, however much you want, and whenever you want. There is no weight loss program in the world that will keep you from gaining weight doing that.
Good luck with whatever program you decide to use!