My Take
I thought there were some students who would never be motivated to do math but I was wrong! I teach in an urban school with a lot of struggling students. I had many of my active boys absolutely love the games on mangahigh. They were willing to practice math facts with no push back or whining etc.
How I Use It
I think this should be used sparingly so it does not become just another assignment. I recommend taking your class to the lab & letting them try the games for free before setting up accounts etc. It really helped my students engage in practicing basic math.