I recently stopped my MathAcademy subscription: I went from halfway through Math Foundations II through to near the end of Linear Algebra. I stopped because I realised I wasn't really learning maths, I was just learning to answer the questions by rote.

The way that they pretty much completely omit all the explanation, proofs and discussion you get in traditional maths education really limits its utility once you get to more advanced content. I think the reason for a lot of the positive reviews is that their approach works really well early on when you're revising the basic end-of high-school stuff.