Here's my three realities that I have developed from personal experience with these "systems":
1. It's one of the highest "barriers to entry" for small shops to expand their markets into things like medical, aerospace, etc..
2. There is virtually no association between actual part quality and whatever kind of system you have received certification for (i.e. don't confuse a quality management system with actual part quality).
3. It's mostly a way for consultants to make money.
What I find absolutely ironic is that all of the basic "features and functions" of a good QMS could be standardized. Customers want a way to reject a part and be assured you've taken corrective action, everyone needs a way to quarantine bad material to make sure it doesn't find is way into finished goods, make sure people know how to read gauges and that those gauges are accurate. That and a few other bells and whistles. Why not just create a few standardized forms and procedures that everyone could use? Well, the consultants (and ISO) couldn't make their money then!
The Dude