Hi Lindago...I have been on WW several times and always lost a pound about every 5 to 10 days. I know that is considered slow to some, but I really think that for me it is best.
I have left WW recently and tried several other diets. They have all deprived you of some of the food groups. And, that is the main reason I am going back to WW and will stay with it. With WW you can eat anything you want as long as you count the points.
As for the flex plan, what it actually does is decrease the amount in your daily range five points. Example: My range is 20 to 27 per day. With the flex points my daily allowed is 22 per day. Then they let you use 35 extra points during the week at any time you wish. You can have all the 35 in one day, or string them out over the week.
That is really great for me. I keep it down to 22 every day, then if I go to a family dinner, or out with friends, I can "blow my wad" so to speak and have something really great, and still lose weight.
Everyone needs to figure out which way to go that is best for them. Any diet will cause a loss of several pounds the first week, which is water and what I have heard called "soft fat".
Good luck...Elizabeth M.