I used it for a few weeks whilst returning to learning German, but have since given Babbel a go and find that much better. Explains the things you need to understand and gives little pointers here and there. The pictures are also very useful when needing to know which you to use (du, ihr, sie..) as Duolingo often expected me at times to guess which it was referring to. Easier for me now and especially if the sentence fits, but at first it was really frustrating.
A mixture of the two is probably the best way to get your vocabulary started, but for really learning a new language there are far better options.