I find Duolingo to be an extremely fun game. My wife and I really enjoy trying to speak other languages and even more so now that we have talking children. I can speak passable Spanish and can string together broken sentences in French to be effective (they get what I mean) and hilarious to native speakers.
Duolingo has never purely taught me a language. If my wife didn't know Spanish and learning French like me, I would have never been able to practice enough in the real world to know.
I enjoy using Duolingo immensely. For me it is a fun way to toy around with a hobby I've had for years without committing myself to dedicated training costs and time.