I also have an ATI FX-45 military model which I bought off Grab-A-Gun a few years ago and I am happy with it. For the money, it's a good weapon.
I've got about 3000 rounds through mine so far with just a few problems. For the first 500-600 rounds, I would get about 1 failure to feed properly and hang up every 100 rounds, but that went away after around 600 rounds. Then at around 1200 rounds, the ejector sheered off from the legs that go into the frame. I could have sent it back to ATI, but instead I brought it to my gunsmith and had him change it out. BTW, he also thinks highly of the ATI guns for general quality too, especially for the price point. Since then, no problems at all. I do plan to replace the recoil spring when I get in from the rig though, as I can definitely feel that the spring is weaker than the one that came in my new ACW 1911 gun. The ACW reminded me of how much harder it was to rack the slide on my FX-45 when I first got it. And I was recommended to change the recoil spring around every 3000 rounds or so.