For my very math-y kids, they seem really repetitive and silly and involve lots of strange manipulations to help the student think mathematically when the student already thinks mathematically. For a less mathy but still GT kid, they have been fabulous and taught deep intuition about math relationships that wasn't second nature already.
I'm not saying these programs are ideal - far from it. I'm just comparing concept-based approaches to traditional approaches. My kids have had the same level of success in their above grade-level achievement tests (>99.9%), so I know it works for some kids.
Many of us have no choice of how our schools approach math education. AoPS would be great, but that's not an option at any school in my area.
