Thank you!
Some people get frustrated by the sandboxing done by the app. Others would like a much longer course that has a lot more detail. Overall it's done well and it's used in many schools, but it's actually quite difficult to make a really inclusive programming basics course that works for everyone. You'd need something that adapts to different people. Also, often, different individuals need someone there to clear specific doubts that block them. I think that's in part why our stuff's used quite a bit in schools and we didn't really get issues reported by teachers - they are there with students in the classroom to clear doubts as they come up.