I gained in my first week and have since averaged around a half a pound a week, but I just kept plodding away.
I think one thing which can make a big difference to the amount lost, is the difference between your former eating habits and the SW plan. If you used to eat lots of fried foods/takeaways/chocolate/crisps/cheese etc and drink a lot of sugary drinks (whether alcohol or pop) then following SW is going to make a huge difference and the weight will drop off. However, if you always ate a lot of fruit and veg, already had skim milk, drank diet cola and so on, the difference is not going to be that great and your weight loss will be slower.
Don't compare yourself to anyone else. Feel pride in whatever you achieve and persevere and keep a food diary - if you have one on here you'll soom make some friends who will help you.