I’ve been using Quizlet for my courses for a number of hers now. Last year I purchased a teacher license ($25 for one year), and I am glad I did. It’s been really easy to monitor progress, avoid ads for my students, and see which vocabulary items are more difficult than other. I can then incorporate hose terms that caused difficulties more into my lessons.
Most students really enjoyed using the tool, including the app. I also replaced quizzes with Quizlet. Students now have to finish learn mode in order to get points (they’ll still get tested a little bit on vocab in exams).
I will definitely keep using quizlet for my beginner and intermediate courses in the future. It’s a tool that is constantly being developed, and that works out of the box without paying for it.