Just to be difficult, the problem is thinking that something is good when it is not.
I'll try to give an example: Getting a file tagged with our uncoated proflile where the file was originally an untagged ISO Coated. I wouldn't have discovered it unless I was checking for too much ink. If the file had not exceeded the ink limit, I would not have noticed it. It would have been technically flawless even though the result would not have been acceptable.
Certified PDF will check and logg events after a certain point, but it is very hard to know if what was put in was correct, so who is certified PDF for? I would think it is for the knowlegable prepress person who hands to a deaf and dumb printer. Or for a printer that needs to proove to clients that they didn't touch their file.