Don Firth, in an informative and thoughtful post, said:

But to fill in the picture, I know a few developmentally delay people (used to be referred to as "retarded") who, if given a job within their capabilities, make diligent, hard-working employees.

A couple of comments here:

"Developmentally delay[ed]" implies that the path of "development" will be the same as in a "normal" individual, except on a slower timetable. I'm not in a position to say that none of the retarded (and that word is really subject to the same objection, I think) will, given enough time, arrive at the same development as "normal" people, but in general it's a false assumption.

Indeed, it is not uncommon for a Down's Syndrome person, say, to take a long time to get to his/her peak, and then tail off substantially from there over time. I'm acutely aware of this because my son Hans, now 30, is far less vocal, far less insightful than he was when he left (supposedly, was graduated from) highschool nine years ago. In speaking with parents of other Down's Syndrome persons, this observation has been frequently corroborated.

Now, as to employment, I will say that Hans works in the laundry of a local nursing home (and has for ten years), and is a valued employee. He's always there, he's always pleasant to everyone, he keeps working and doesn't goof off, does a good job at the admittedly simple function to which he's assigned. He gets good job evaluations on everything except speed of work--but they knew that and were prepared to accept it when they hired him.

Dave Oesterreich