There is absolutely NOTHING special about Imron today.
Yes, 40 years ago, it was the first true urethane paint. And, it was different from other paints.
Today, every major paint company has a high end product, that is just about as good as the other. All are FAR superior to the original Imron product.
I worked in the business for 35 years, and sprayed them all. Including the original Imron product, which had some serious short comings. It was very slow drying, especially in colder temps, was really bad smelling for days, and was not easy to repair, without wrinkling. It had one advantage, it held a very high gloss.
Could it actually meet the, "bullet proof" standard everyone believes it had, or has? Nope. Even today, no high gloss automotive refinish product is anywhere near bullet proof.
Much of the durability in a finish, has more to do with what is used under the paint, and getting the undercoats, and top coats, to bond together on a molecular level. It's a little complicated, and a lot expensive.