From the bodyshop side:
You have to understand that the insurance industry and their policies and practices are changing all the time.
At one time, State Farm was the worst for specifying aftermarket parts. Following the class action suit, they did a 180, and specified used or OE on everything except radiators and condensors, and common mechanical parts that usually are sourced through the aftermarket anyway. We'll see how the court's overturning of the class action settlement affects their policies shortly, I imagine.
Progressive just flat out sucks. Aftermarket everything , and it doesn't matter if the car has 100 miles on it, it's going to get aftermarket. Geico is just as bad. You must understand that these companies are able to discount their rates for a reason, and that it's not going to be that they settle for less net profit. Aside from paying their personnel less, the money has to come from somewhere.
Farmers currently sucks...aftermarket everything, and constant arguing over judgement times on repairs. They also don't particularly care about the long-term viability of a repair, or if repairing a panel is a lesser repair than replacing it (we're talking weld-on panels here).
Allstate, despite their generally poor reputation, isn't too bad, as long as you are not on the "PRO" (Priority Repair Option) program. In fact, the local office routinely writes to replace items that we as PRO shops would take major crap over writing. I guess when they have to deal face to face with the consumer, they prefer to avoid possible confrontation.
God help you if you have to deal with one of the myriad of smaller companies...guide 1, Atlanta casualty, farmer's union, dairyland, country companies, etc. They usually use an outside appraisal service, and endlessly haggle over every little item.
Now, having said all that, you also have to realize that there are good people and incompetent people in all these companies, and many are not happy with their situation. Add to that the fact that most every shop or consumer they deal with assumes they are an idiot , a liar, and a cheat, and it's not too hard to understand why they tend to be on the defensive. Our Farmer's rep is a decent guy, but corporate is busting his balls over every little thing, and it unfortunately trickles down to impact us at the shop, whether it be attempting to repair a panel that you know isn't going to repair, or arguing over betterment on tires, batteries, etc. Operating policies and how they are implemented also vary from area to area, even within the same company.
I have a very good friend that works as an adjuster for Allstate, and though he is well-paid, he's building his own business, because he said it's obvious that the industry cannot survive if it continues operating the way it is now. Of course, he tends to apply logic to decisions made in the course of his job, and that doesn't sit well with management. They also resent that he actually knows something about automobiles, as apparently most mid-upper and upper management do not.
As to the actual topic: Farmer's will not allow you to carry just comp on a vehicle in Oklahoma, apparently. I tried a couple of years ago. Didn't matter a bit that the car was without engine, had to carry liability to keep the comp.