I believe that WW is all about lifestyle change (the accountability is important, too).
The only thing really discussed at WW meetings is how to stay on your plan. Everyone at the meeting has individual points plus assigned to them. Points are based on age, weight, height - just as fitday figures your calorie allowance for you. Points are basically calories, weighted a bit to steer you toward fresh fruits and vegetables and some lean protein. You can also earn points with physical activity. At a recent meeting, I saw that WW has a pedometer that not only tells you distance but also how many points you used in a day by walking. You don't have to use it - it's just a convenience. I don't use activity points to try to be able to eat more, but it would be good incentive to exercise if I did.
TOPS and Overeaters Anonymous are cheaper but they have the necessary components of support and accountability. If you use fitday faithfully, there is support (forum) and accountability (reports of what you accurately enter). One thing that WW adds in accountability is automatic logging of your weight from the meeting weigh-in to your online profile (Weight Watchers online). Your weight goes into the computer from the weigh-in and appears in your weight report when you log in to WW online.
One thing I have noticed: when I eat to stay within points range, there's not so much food in my kitchen. Whatever the cost of WW, if you stick to the points, you definitely save on food. Fresh vegetables and fruits can be expensive, but I buy marked-down veggies, past their prime. They taste good, they are fresh! I imagine this would be the case with TOPS or OA, too.