I am new to SW.
The idea is not so much a diet as a lifestyle change - changing your relationship with food and breaking bad habits.
You can eat loads on SW, you are restricted to 15 'Syns' a day though.
Fruit, veg, eggs, pasta, rice, potatoes, lean meat, all free on the Extra Easy plan (I don't do Red/Green days so can't comment on those)
Certain foods are Super Free or Super Speed - meaning if you eat more of them, they will aid your weight loss. These are all fruit and veg (starchy fruit/veg tends to be 'free' rather than SF or SS though)
You also get to chose (on Extra Easy) a Healthy Extra A choice and a Healthy Extra B choice. All are listed in the book you are given.
A choices are dairy - all kinds of cheese, weighed.
B choices are wholemeal bread (2 slices, 400g small loaf), sensible cereals (ie not Cocopops!), nuts, dried fruit (again weighed)
An example of Syns.
125 ml wine = 4 syns
A Galaxy Ripple bar (33g) = 8.5 syns
1 slice wholemeal bread (from standard 800g loaf) = 4 syns
There's a lot of online support, Facebook groups and the actual SW website.
I lost 5.5 lb in the first week, 1 lb in the second (did have more Syns than I should have) and maintained this week - it was my birthday week and I did have wine/chinese/cake though, so what can I expect lol!
I think it's great, I have tried lots of different recipes that I'd never heard of or dared to try before (diet coke chicken being one - yum!)
You really do have to eat all your SS and SF fruit and veg though, that's how it works. You'll think you won't lose weight but as long as you are snacking on healthy stuff and really watching what you are eating in regards to lean meat, no (or little) sugar, then it really works.