I like the app. Its a decent reference and the quiz can be either multiple choice (easier) or not (good for really testing your knowledge).
My biggest complaint is that the app has sound effects that add little value, and make it impossible to use the app while listening to a Japanese podcast. The app should have a way to disable the "click" sounds during the quiz.
Whisketjunket about Dr. Moku's Hiragana Mnemonics, v2.1