The fact that there are only Italian and Spanish wines in this app is a big limitation for a novice wine drinker looking to gain a more sophisticated knowledge of a broad range of wines that might be commonly available in the US.
I am assuming geographic areas will be added with further updates. In the meantime, the general information about grapes, and the descriptions of wine terminology and concepts are helpful irrespective of the selection of wines the app has (for now).
pd-defender about Approach Guides Wine Guide for iPhone