I agree with Scarlett, i'm not denying you can have tremendous success on it, but it does encourage bad eating habits - namely overeating.
I tried it, but i got bored, although you can be flexible i found i was eating the same things constantly, no matter how much i tried to vary my diet. My sister in law is married to a slimming world leader, and she is always moaning about eating the same boring foods.
I had much more success on my own. Lots of websites do free healthy meal ideas and exercise plans for beginners. I'd save yourself the monthly fee and go it alone, if you can. If you're worried about lack of motivation, maybe you could buddy up with a friend or family member and you can encourage each other.