I'm a SW member too!
Whilst you *can* eat unlimited pasta and potatoes, you still have to follow the 1/3 speed food rule if you wanna see steady losses.
(1/3 of every meal should be speed fruit and veg, there's a list of these in your book)
SW really just works on a balanced diet and on not depriving yourself of anything you want to eat. I did low-carb before SW and though I lost weight quickly it just wasn't all that sustainable.
With SW I lose about 2lbs a week and can eat pretty much anything, in moderation.
Plus, pasta and potatoes get boring when you can only eat them in SW approved ways- i.e no butter, creamy sauces, proper frying etc so the novelty wears off!