Overall the app is a good way of learning or reviewing a language. I have been using the Spanish in order to brush up on long unused high school/college Spanish. My wife has been using it to learn for the first time and loves it. For someone who has more than a basic understanding of the way the language is structured I think there are some issues. I do not like how verbs are first introduced without ever explaining conjugation. Verb conjugation is one of the most difficult aspects of learning a language and should be taught at the beginning rather than memorize individual words. Also when translating the sentences the first word is always capitalized which allows the learning student to always start off with the first word correct. There is no learning it is given to you. Otherwise it accomplishes its intended goal.
Army_of_Anubis about Duolingo Learn Many Languages for Free, v5.0.15