Another reason I have issues with this math website is that the skills do not transfer. The look of the website is very "cutesy" and looks a bit like a Las Vegas version of Club Penguin. Lots of sounds, animations, bells, whistles and froo-froo. In my opinion, my third graders need REAL math skills practice, with instant feedback on how they are doing with a minimal amount of practice time.
DISCLAIMER: I am NOT an educational researcher!
There are some really great websites out there, many of them free or super cheap. The one I discovered and really like is called IXL.com. They have a 30-day free trial that you can sign up for. The platform is VERY clean and the students can get instant feedback on their progress. (In the annotated screenshot below, the students' view would not have all the red boxes.)