So I don't really have much to say about this, not having tried the Japanese module specifically. I'm just posting as an FYI, because someone somewhere some time asked me about free/low cost online resources for learning Japanese (I'm not even 100% sure it was on this forum--my apologies if it was, and I can't remember who you are!).
Anyway, Duolingo just added Japanese-for-English-speakers to the latest update of their free app. I have actually used Duolingo for other languages, not really to acquire proficiency, but just for fun, so I can say that I like the general platform and approach, at least for someone with a casual interest in a language. I also have friends who are language teachers, who do find it to have some utility, and enjoy the gamified elements.
