If you're referring to the "Kid's Night Out" service, I can only say we've used them on 4 or 5 occasions and we've had nothing but wonderful experiences. The sitters are professional, and show up in your room with toys, games etc. The transaction is documented with a detailed contract, and the sitter wears a little vest that identifies her. My wife is a self-described neurotic about our children, and it was hard for her to leave the room the first time (when our daughter was a year old), but she's never had the first complaint. We've always requested that we be given one of the service's more experienced sitters, and they've always agreed to do so. In fact, on one occasion one of their veterans showed up accompanied by a trainee; my daughter was in heaven. She had two people to ham it up with.
You're right, they are not Disney employees, but it's the only in-room sitting service that Disney recommends. They don't want to lose that relationship, so I think the company bends over backwards to do things right.
