I really like the focus on watching or listening to source materials every day. This is where Duolingo fails, or at least how my SO uses it. It becomes a game for listening to snippets and remembering vocabulary, not actual comprehension of language spoken by native speakers.

For anyone who is a student, I highly recommend the National Taiwan Normal University (師大) Mandarin Training Center summer sessions. The materials are developed and taught by well-trained teachers. It's completely immersive in the classroom, and it can be applied on the street every day you're there. They have programs for younger kids and middle school students (which my kids took some years back) as well as college and graduate students (http://www.mtc.ntnu.edu.tw/eng/course-seasonal.htm).