I've been on Weight Watchers for over a year now, and I've lost 70 lbs on it so far. Personally, I love the program. It teaches you how to eat healthily, without being so restrictive that you can't have the occasional cheeseburger.
I've found it to be very liveable.
I was scared at first of what the meetings would be like, but I actually really enjoy them. Nobody knows your weight except you and the person weighing you in, and they're very discreet about it. They don't make you feel bad, even if you have a bad week and gain a few pounds. (Heck, we ALL have the occasional bad week and gain a few pounds.) The meetings are more educational...talking about how to keep focused, what works and doesn't work, and tips from each other to help keep on course.