I've been using Duolingo everyday for 2 months now (to learn Spanish). Some thoughts: It's entertaining. You don't need much motivation to "play" everyday. Whenever I want to procrastinate, I feel it's a better option than reading the news and so on... However, it's too simple (which is why it is addictive). By itself, it's not enough to learn a foreign language. It's a good complement, and a great way to get started though.