I've been doing it for a week. I've lost 5lbs in my first week. In all honesty, I think you could be just as successful calorie counting; the only reason I joined was for the motivation of being weighed in each week. That, for me, has helped me get out of a several month long rut of not being able to motivate myself fully.
I have read many negative reviews on the weight watchers website about putting on weight on the new plan but so far I've not had any problems.