Never had exchange students but I have had "stagiares" (kind of like interns). They come for a summer job, rather than for a school year. All experiences so far positive - perhaps people looking for work are different than people looking for school, although the ages and backgrounds were, I'd think, similar. We've had several Frenchwomen, a Turk, and somebody from somewhere that used to be the Soviet Union. All spoke some English, which I would think would be an absolute requirement for an exchange student - what do they expect to learn in school if they can't follow the lesson?

Bottom line, I've heard horror stories too, but a) they are more fun to tell than success stories, and b) they are far outnumbered by those success stories. I'd say Worth The Risk.