Hi James,
of course not every printshop is incompetent. But I’m a printing engineer who knows the PDF specs as well as their application in prepress. I used to work in printshops and prepress agencies most of my professional life (now self-employed), and often had to prepare data for the printshops that my customers chose. A big one e.g. requested PDFs as single pages with all text transformed to curves, others didn’t want bleed or didn’t manage to keep 100% size (because they "printed" to film using Acrobat’s page size adaption), color management is over the head of most (I know it’s difficult, but you can’t avoid professional knowledge forever) etc. And "of course" they don’t understand the error messages of their workflow software … :-(
I stop here since it’s off topic on this list, besides ranting doesn’t help anyone ;-)
That's probably true about the ranting, but it's also nice to know that people here have real industry experience with this matter! So, thanks to all of you who know about this kind of stuff, for being here to bounce our questions off of.