They really are amazing: about 1cm square in cross section crunchy and crispy on the outside, but not overly so, light, fluffy, and the perfect balance of dry/moist inside. Never oily, always cooked fresh, and without exception, delicious. Though I will confess that I never got behind putting Mayo on top.
Anybody fooling around trying to replicate the original McDonalds recipe is shooting for the wrong target. Shoestring fries don't have the inside/outside texture contrast that makes for fry perfection.