I am lifetime WW member, lost 40kg first time round and have returned many times. My theory is it works best the first time because it actually teaches you things, once you know what your doing it is much less bang for your biuck
What it does do is make you accountable as you front up to get weighed. But it is an expensive way to be weighed.
What I think is a better use of money is personal training sessions. Ask them to weigh you, then they also get you mobving,,They do know about nutrition but you know what your meant to eat etc already, its just a matter of doing it!
Good luck!