Controlled feed is the 1911's greatest strength and greatest weakness; when parts are in spec, the controlled feed mechanism produces an autoloader that can be fired from any angle with almost any ammunition while producing revolver-like reliability. The downside is that magazine design plays far more of a role in reliable operation than in other guns. It's not really fair to say 1911s are magazine-sensitive, though, since few other guns can boast the range of magazine designs inflicted on the 1911. Recent complaints about the M9's unreliability under desert conditions have widely assigned blame to the cheap aftermarket magazines provided, and I suspect even the vaunted Glock reliability would transmogrify into the 1911's jam-o-matic reputation if Glocks were also saddled with the expectation they would feed from anything capable of being jammed into the magwell.
