Certainly know of it, but I am not familiar with its approach. Fleur, as a linguist, would you mind giving a condensed pros and cons critique of Duolingo's modus?
Well, I'm not a linguist, Heinrich, but based on my own experience, I would say that the biggest weaknesses are the use of translation, which keeps you tied to your first language and inhibits the second language system from developing, and the lack of opportunities to use the language creatively. In order to internalize a language, you really need to use it in ways that are personally meaningful.
Despite that, I find that I am able to learn using the program. Duolingo's approach uses implicit input and spaced repetition. Though you can access explicit grammar explanations, the idea is to present you with a series of sentences from which, over time, you can pick up the patterns. The amount of repetition needed to internalize the grammar this way does become tedious, as aquinas mentioned, but it is effective.
Over all I don't think that Duolingo alone is a very effective way to learn a language. But combined with other sources of input, such as videos and readings in the target language, and a concerted effort to use the language creatively, by speaking and writing it in real-life contexts, it can be a useful tool.
