How I Use It
My wife and I don't use it to teach our children. But we are also part of a community homeschooling group that does use it with our children.
From our perspective this program is not actually teaching them much. It uses a lot of repetition and seems more focused on memorizing answers. My 6th grader prefers Khan Academy since he feels he is actually learning math concepts there, With DreamBox he feels he is just clicking through games and has to get things wrong first before it gives any clues on what to do. And even then it just gives him the answer so he can get it right next time. He is frustrated that it doesn't ever explain what he is trying to accomplish.
My 5th grader loves it. He plays it all the time but we are not sure it is actually teaching him much. For example, he has recently been working for a while in DreamBox on fractions but my wife noticed he wasn't really getting it. She decided to give him a quick lesson of her own--his response, "Awesome, now I know how to beat that DreamBox game".
I plan on doing a bit more research to make sure they are using it correctly. But I really trust my 6th graders opinion on this. Maybe it works better for younger ages. As a review or assessment tool, it might be great. I have not seen the back end and what is provided to the teachers.