I dunno. I'd say "Rain Man" is fairly accurate. Of course, they're going to Hollywood it up, like they did with "Forrest Gump," but I've seen people who had that condition, and they acted a lot like Dustin Hoffman in the movie.
These people tend to be very routinized, and they get extremely agitated and anxious when that routine is disturbed. The routine is often what gives their lives structure and meaning and they are lost without it. Most of the time, they do need to live in a group home environment, where the staff can make sure their routines are very regular and can prepare them for any special events.