This app sucks. Plain and simple. First of all, this demo only quizzes you on 25 states, so in order for it to actually be somewhat useful you have to pay them $6 for the full version. Well, that's fine, if it was worth it.
The quiz provides you with a state and four or five choices to select from. Because of some poor randomization or something, you often get the same states over and over. I got Alabama six times in a row before it would move on to another state. I imagine to actually get quizzed on all the states would take hours. Many times the question would not even provide a correct answer.
In summary, this app sucks. I was going to use it to freshen up for a geography quiz, but it seems there are much better alternatives provided for free around the internet. Your $6 is better spent on a map. Or a cheeseburger.