I had a subscription to Cathe's nutrition program last year and used fitday and sparkpeople before. Whereas I really liked Cathe's program like others I started obesessing over getting As, spending way to much time playing around with it and thinking about food.
I personally do much better if I don't use any of those programs because when I do it makes food the center of my universe. I ended up totally changing my diet and not counting calories, protein, fat or carbs at all and it's the best thing I ever did for my weightloss and fitness. Everyone is different though.