Not worth the time. The initial screening process was quite nice. They gave me a "take home" programming assignment of which I was to fetch a file from a server (the directions were very vague on how to store said file), display some content contained within a file, and execute some game based with a self defined UI (the directions were vague on how the UI was implemented).
The screener said that it would take 10 - 12 hours to complete the assignment. It did end up taking me about that long to do it in an object-oriented, well organized way. The quick and dirty way would take around 4 to 5 hours if anyone is interested to know. After spending said time and waiting for a reply, I was given the old "you're not what we are looking for, thanks" message. When I inquired about feedback, they were unwilling to provide me with feedback. I know that I may not be the best developer in the world, but, generally, if you are going to ask candidates to put in 10-12 hours of their life into your interview process, then you should give them the common courtesy of feedback. In my short 8 year experience in the field, I've never dealt with a company that cared so little for a candidate's time and energy. Honestly, that's what compelled me to write the review. If this is how they treat prospective employees, then you have to wonder how people are treated within the company.
Just don't waste your time with the interview. There are lots of other companies, such as LinkedIn, Pandora, ect. , with robust technical interviews that will at least give you a little something for your time. I've taken some jobs from these and been denied by others with something that I could learn. I'd just skip Duolingo completely. Have some self respect as a professional and don't waste time with those that don't value yours.
Thank you very much for reading my experiences and review. I hope it helps someone.