When I started using Duolingo, it was great! However, in the last 2 years, they've increased the frequency and duration of third party ads, Duo premium ads, and progress animations (an utterly useless feature) following each lesson. I can accept dealing with one ad per lesson; however, 2+ multi-second video ads with 2+ multi-second progress animations eats up way too much time. Also they changed the entire curriculum for my language last year, losing all my progress.