One feature I find interesting, is that you have two choices of ending. One is to show the participants score. The other is to allow the participant to add a question. I think the latter could be powerful (or dangerous) if used with students.
Participants do not need to login. However if they do have an account and login, the results of registered participants appears filtered out from the anonymous participants. As per usual, registering requires an email address. However, registration is instant, no need to confirm registering by clicking a link sent via email. I didn't try registering with a linked Gmail account. If that works, it could be used with elementary students.