I talked to one of the authors of this paper at ICLR and he said that it wasn't really worth the time to compute the adversaries and train, though it did improve results. He said that in the time it took to generate adversaries and then train on them, the net was better off just training on more image data, since there is a near infinite supply of it. Perhaps if you didn't have an infinite dataset, this wouldn't apply.
Also, the really interesting thing was that adversaries generated for one network topology/data set were still adversarial even for other network topologys/data sets, which might imply that the nature of the adversaries is universal rather than highly specific to that exact network trained