The research fail that jumped out at me hardest in Atlas Shrugged was the idea that so many people would consider a metal both stronger and lighter than steel physically impossible. By the time the book was published, not only was titanium fairly well understood, it was also being widely used in military and (some; what could be spared from Cold War efforts) commercial purposes. Its properties don't exactly match Rearden Metal (even ignoring the color and other mostly-unimportant characteristic) but they're close enough that it should be obvious that such materials are completely possible. Of course, that part of the book also talks about making steel rails last longer by making them denser, which seems completely bizarre to me; there are ways to increase the hardness of steel, but they involve things like heat-treating it.

TL;DR: I'm not sure I'd call the book "well-researched" as a whole, though some parts may well have been.