Here's one for ya...
My good friend got Willys Jeep. It was a rough project. After removing the body and realizing it wasn't worth repairing the rust and damage, he decided to continue the restoration on the chassis/drivetrain. He stripped the tub and sprayed it down with a cheap primer, and some base coat that was on the clearance shelf at the paint store ($10/gallon). He took the tub with him to Georgia for Thanksgiving holiday since his little brother works at a truck accessory shop that does Line-X. Just for fun, he had them spray half the tub with Line-X inside & out and left the other half bare. When he came back home to Texas, we sprayed the other half with Herculiner from Autozone with a Shutz gun we got from Harbor Freight. The two liners looked a little different in texture, and the Line-X stayed a little glossier than the Herculiner, but even after 4 years, there was no noticeable difference in wear. He took this thing offroad, hunting, left it out in the weather, through thick brush, etc. He finally had enough dough to get a rust/dent-free tub and sold the lined tub on craigslist. After that I was sold on the cheap Herculiner and since then we've both done our own pickup beds with the stuff, and I've done the insides of a few FJ40's and Willys Jeeps for customers, as well as a full body spray on a rock crawler Bronco for a guy. In my experience, it's all in the prep work...just like a paint job. I charged $450 for the FJ/Willys Tubs, and $950 for the Bronco, and that was all due to the amount of labor involved. I've seen the Bronco twice since then and it still looks as good as the day it was sprayed 2 years ago. Only the rock sliders and a few parts of the bumpers and lower body sides have chipped or peeled off, but that's because of the mashed up metal beneath the liner.
Speaking of the Herculiner stuff, I'm about to do the bed and bottom of the body on my '94 Chevy K1500 and the bed & floor of my '83 F250 project.