In the carpentry forums, they refer to drywall screws as the 'duct tape' of the fastener business. I don't use them, but I can't say I get upset when I see one used - especially on a plastic box.
I do object to their use where they mess up the threads in a piece of metal.
I have absolutely no problem using drywall screws as a general-purpose way to attach boxes and straps to wood framing. Or, for that matter, to light steel framing.
It has been my practice to have an obscene collection of hardware on my truck, including all manner of fasteners. While the supplied hardware is usually adequate for a job, sometimes you need a longer screw, or to replace a missing one.
I've been busy recently, repairing damage to a flooded basement that my Dad (and brothers) finished themselves. Let me put it this way: of all the electrical 'sins' committed -some quite 'legal'- the occasional use of a drywall screw to hold a receptacle to the plastic box was by far the least worrisome to my eyes. For example, i think it's really much nicer if the romex jacket makes it into the box, and I really wish they had not back-stabbed their daisy chains together.
Indeed, if an inspector missed the short jackets, but harped on the drywall screw, I'd want him to find a new line of work.
