My kids found Dreambox much more interesting than IXL. With IXL, the child is incented to answer all the questions in a grade level, even if some of them are way, way below level. Furthermore the questions are all drill.

With Dreambox, by contrast, there is an algorithm which suggests different exercises for the child based on their speed and accuracy in answering the questions. There is also much more variety in both how the problems are presented and the graphics involved. Up to about grade 3 math, it is a lot of fun.

That being said, my kids both got bored somewhere in grade 3 and 4 as the exercises got somewhat repetitive. It was good while it lasted, though.