Solid class. Dorian isn't necessarily the friendliest or warmest professor, but he does a good job of explaining some fairly complicated concepts and is fairly reasonable. The class covers cryptography and coding theory and the math behind them -- they're fairly interesting topics. He stresses this in the first class and he's right: the class is much harder than the first week or two would make it seem. The first few topics you cover are pretty easy and then things really take off. The sense I get, however, is that it's still easier than most upper-level math classes, though it's not a walk in the park by any means.
One huge plus is that Dorian reviews the material a lot. In addition to the review sessions he gives before the second midterm and the final, he starts off each class by reviewing everything he taught in the previous class. This can be a bit tiresome if you're on top of everything, but it's great if you ever miss a class or just feel like you've fallen behind. He also writes an insane amount of notes on the board.