I can only speak for the airline industry. I'm a pilot. I don't work in the other areas, so I'll stick to the airline industry.
SMS, from what we've seen so far, has worked very well. It has led to changes in procedures that would never have happened, unless the pilots or the engineers or whoever works around the aircraft, came forward and identified this potential problem or this error that continuously happens. This would never have been fixed, and the worst-case scenario could have happened. It could have led to a serious incident.
Because of the SMS system, those individuals involved were able to come forward with the information, with no fear of any retribution. It was discussed and the problem was identified. In some areas, it was just a simple matter of changing the order in which a checklist was done. So from what we have seen so far in the airline industry, it's all positive.