We have both Dreambox and BrainPop for my DS8 (and BrainPop Jr. for DD6).

DS liked Dreambox for the first few months, but it became very repetitive, so he's pretty much stopped using it.

DS loves BrainPop, although I agree with a previous poster that it can be somewhat superficial. But it's a great way to introduce a topic that we might not otherwise cover. DD enjoys the Jr. version, but I find it to be way too simplistic; next year we'll just get the regular version.