I did weight watchers many moons ago when I was a teenager. It is really good as the plan fits into your life, and teaches you about portion sizes, what to eat, calorie control etc. 18 years on I still use what I learnt there, even though the program has changed a lot since then.
I gained all my weight back, but not because Weight Watchers failed, I did. It's long and complicated and I won't bore you with it all.
Now I am losing the weight on my own, with help from the staff at my works gym who run a weight loss program. I don't like group weigh ins, and I do get trapped into comparing myself to others, which in turn makes me give up. Psychologically I am better without the support of others in real life, and use this site as my main source of weight loss help.
I think the biggest battle in weight loss, is finding out what works for you as an individual. We are all different, with different needs, and it took me a long time to understand that!