I acquired one of these a few months ago. It's my understanding that the 590A1 has been discontinued...or, rather, that its mil-spec features have been adopted by one of the standard 590 variations. In any case, I got the parkerized 590 with ghost ring sites, and bayonet lug.
I like it a lot. I haven't had much chance to shoot it, but I have taken it out, and it's just dandy.