I've been doing it for 8 weeks and have lost 8lb. I have about 1 1/2 stone to lose all together. I joined online which was £80 for three months membership. You don't go to classes but have access to online forums with other members, all the information, loads of recipes, plus they send you the books and a magazine every month. Then you have to weigh yourself once a week and log your weight online.
The diet I'm finding very easy. It's no longer the red and green days. They've combined that now so you can eat as much as you like of pasta, rice, veg, fruit, fish, and lean meat. Wheat and dairy is limited to one portion a day, then there are syns for treats. It takes a bit of planning to make sure you have the right foods in the house and it means cooking most meals from scratch, but if you are prepared to do this then it is easy. No need to feel hungry. Iceland also sell SW ready meals which are nice.