I finally got the 590 parts in the mail. The upgraded trigger assembly is a nice addition. It does have a stronger hammer spring, a slightly heavier pull and a slightly harder action now, but its now spec’d to 590A1, minus the bayo lug. You can see the difference in the 500 polymer assembly and the metal one.
Another thing that was a pain in the ass was removing the old safety button. Its a one-way screw, but after using a hollow ground flat bit and some force it came out with minimal damage. I installed the metal safety with no issues.