I don't for one moment thing interacting with my phone will give me another language, but doing wonders for my confidence. Can just throw yourself into it at great velocity, and if you fuck up, it doesn't judge and just throws up those same hurdles until you clear them.
Time has also cleared another hurdle - I've now got loads of access to French in a format I want. I can watch netflix in english with french subs, and then switch to french with english subs. Previous time I tried this, was watching La Haine on VHS from my local library. A great film - but didn't overlap too much with the french I was taught at school (Somewhere out there, I like to imagine there's the friendlier "Le n'aime pas" version)
What I would be interested in, is the best place for the next step - being forced to talk to a real French speaker.
Maybe my favourite bit of Duolingo, is the mini-forum attached to each question. It's a little bit hidden (as maybe doesn't align to their smooth-app-experience), but found it invaluable when I'd screwed up to be told why. So many times I've clicked full of rage at being told I was wrong, and not only learnt why I was wrong, but got a proper explanation that's stuck with me.
Maybe that's my main Duolingo quibble, the never-ending-pop-quiz is great, but it maybe over-simplifies. I'd like a tables showing all declensions, or a paragraph covering why nobody uses Vous any more.