Mags
I own lots of 1911s including two Rock Islands and two Taurus guns. I like bargain guns as well as my higher end Kimbers. There is NOTHING that my Kimbers can do that my Taurus or RIs can't do, as well or better. I have looked at the ATI compact and, in my humble opinion, it is a well made gun that is on Par with the Armscor guns. I don't like railed guns but, the gun that you are looking at is a LOT of gun for the money. It has basically all the features of the TRP, which costs more than twice as much. Personally, I would take the chance and buy it. Six hundred is not a lot to spend on a 1911. I will put in another vote for the Taurus if you decide against the ATI gun. Both of mine have been incredibly reliable and accurate. It is in the same price range as the ATI. The only differrnce is that the Taurus has fixed sights and no magwell.
Consider this, even if you do have issues, most competent gunsmiths can get any 1911 to run reliably for minimal cost. Since you have just about every toy imagineable on this thing allready, about the only thing you might want to consider is replacing some of the high impact parts with non MIM parts. By the way, even companies like S&W, Kimber and Springfield Armory use MIM parts, with pretty good results, so it is not neccesary, but some people like to swar them out as they can afford it. I have not bothered with any of my pistols.