As far as I can tell from forums, it's not like 5% have the side effects, it's like 80-90%.
But for the first time in decades, I felt full. I didn't want to finish a meal, it was too much.
My body regulated my food intake in what felt like a natural way.
I hadn't even realized my body had somehow lost that fundamental mechanism of appetite control. It made me realize I wasn't weak willed, something is different about my body than other people.
But it comes with a price. The side effects I had were quite bad and so I stopped (though I now read that if I switch to a different brand, I might be ok).
I often didn't want to leave the house due to a dicky tummy. It could come/go in waves. But often can last a whole week.
Plus you've got to inject yourself every week. Often you can't drink as it makes you sick. Even when you're doing everything 'right' you can feel a bit off.
If you do over-indulge (with food or drink) the side effects can sometimes be massively amplified and you feel terrible for days.
So amazing in some ways, but it's not like taking a vitamin tablet. There are costs and making one slip up can result in suddenly feeling awful for a day or two.
Perhaps I was just particularly prone to the side effects, but it seems to happen to a lot of people (I found Mumsnet threads about it useful, they are quite revealing as they seem to be fairly honest and willing to share their experiences)