My Take
I am yet to find a resource that is as good for helping students with automaticity. My students willingly answer thousands of questions outside of school. Students can add friends and compete against each other. I love the adaptive nature of the questions and that as a teacher I can adjust the skills. I've been using this site for two years now. I appreciate the regular improvements they've made.
How I Use It
My students beg to play SumDog. I've used it for early finishers and during centers. Students often choose to play outside of school.
We have subscriptions for our students in order to allow us to create competitions. In addition to class competitions, we have a school wide Math March Madness Tournament.Using the "team" feature of the competitions, classes compete to advance to the next round.