Not me, but my stepbrother had RNY bypass about 5 years ago, in his mid-thirties. Since then, he has maintained a 100+ pound weight loss (top weight of about 350, and he maintains between 210-230 these days. Not swimsuit model, but much better.)
Yes, he has to be vigilant about his diet, supplements, and alchohol intake (Bryan + one margarita = funny!) For him, though, surgery was the difference between maintaining his family, career, and life in general vs not. He is a medical professional, and researched the options a lot before deciding which was best for him, but at the time he had the surgery, he was very near the point of being physically disabled due to weight-related complications. (And, like my stepdad, Bryan previously had great success at losing weight, but was unable to keep it off.)