My Take
I think it is a great tool. It is immediately engaging--don't forget to turn the sound on--and great for instant feedback. It could allow for more characters for each question, and offer some non-login quiz creation for students. My students mentioned they'd like to use it to make quizzes for their classmates. For now I'm planning on allowing them access to create literacy circle questions.
How I Use It
I have only used this product in vocabulary review, but my students are dying to use it more. I have 3 students for every connected device and I don't want to create a negative environment around a fun feedback/review game. It works as a quick practice and review of material. It doesn't work for longer questions, or in my case questions in two languages. It has a ceiling on amount of characters for each question.