Useful but limited.

JapanesePod101 is a great podcast produced by ILL (great acronym!), the company that makes this app. I think they really missed the ball releasing this app with such a limited vocabulary set. I have a premium subscription for their podcast, and use it everyday. It is excellent and well worth the money. When I first read about this app I bought it right away thinking I would be able to use it review all the vocabulary I am learning through their podcast, however, most of the vocabulary from the podcasts cannot be found in the vocabulary list in WordPower. The words in WordPower are useful, but having it complement their online course would be much more so.

GarySaville about Learn Japanese - WordPower