Well, I'm more likely to get laid even if I'm ugly or overweight. :P
But really, in my last job, most of my clients were developmentally delayed. They were also really awesome people and I adored working with them. That being said, I've seen how challenging their lives were, how much assistance they needed, even with things we take forgranted, and how many things they would miss out on in life. While I love and respect all my clients, I would never choose that for myself or anyone else.
I think people think mentally challenged people are happier than most other people. They seem to experience a whole new level of joy that most people will never see. I don't know if this is true or not, but it seems to be the general perception. People who do not like their looks, however, experience low self esteem and depression.
So who the F cares about what I can or cannot do or what people think of me as long as I'm happy. When it all comes down to it, I'd rather be happy than sad.