Wow, I guess this is why so many of us like this website. A LOT of really good information.
For many years, I not only did not own an adjustable, I would not allow anyone to bring one into my shops. However, for the last 30-odd years I have also worked with a bunch of sparkies, and anyone who does that knows their tool kits all contain a couple of adjustables, a couple of slip jaws, a really good pair of lineman pliers and side cutters (the last two almost always Klein). Being the "tool-and-fastener-nazi" I chide them every time I see them use the adjustables or slip jaws on a hex fastener, and they all shoot back some poor excuse, but in reality, these guys are carrying in one bag enough tools to do a thousand different jobs.
While I have never actually purchased one, over the years leftovers from jobs accumulate in my mobile tool box, and I have to cull it from time to time to keep it from being stuffed, and a fair number of adjustables from 6" to 18" are hanging around the shop. I will keep a 6 and 10 in mobile equipment for obvious reasons, but have to comment that when the sparkies hand me their stuff, it is usually made from Chinesium and won't hold an adjustment to save its life. The other thing I harp on about is using such a wrench backwards. One of our crews experienced my making formal complaints about a subcontractor using one on critical parts, and worse yet using it backwards (risking the nuts and bolt heads, never mind his knuckles). The guy went ballistic and simply refused to use a proper wrench. Before I could find his foreman, a few (large) nuts later, his mickey-mouse China **** wrench being used backwards rounded a nut and smacked him square in the mouth, breaking a tooth and resulting in a site incident investigation. At least the our crew with me is to this day VERY careful about using decent adjustables correctly.
Once again: NOT an area of tooling I have any real expertise with, so thanks ever so much for this thread. It deserves to be sticky.