I’ve been using Duolingo “religiously” for 9 months now to brush up on my Spanish. It has helped me improve my grammar and vocabulary, but that’s about it. The daily minimum goals take about 5–10 minutes, which is not enough practice for me to retain much. It does not help me read or listen to large amounts of Spanish. And it doesn’t require me to speak or write more than one non sequitur sentence. My Spanish speaking colleagues have tested my ability to have a conversation, and Duolingo fails to support me there. It’s great supplementary material, but Duolingo alone won’t get you anywhere if you don’t put in extra effort.