I have it in the Android version - it is a good "resource" and I think most archery-season elk hunters could learn something useful from it. And for $5 (the price of a sandwich, or a magazine, or just over a gallon of diesel), it is not something to get too worked up over if it doesn't impress.
After buying it and playing around with it, if I had it to do over again, I would. It is actually a pretty well-built dichotomous key covering a wide variety of hunting scenarios, and Chris Roe knows what he is talking about when it comes to elk behavior and hunting/calling strategy.