My DS liked playing with his friend's twist & shout math game, so we bought him a turbo twist for Christmas. I thought that would be better because you can buy the extra cassettes to keep it "fresh" for the kids.
We got one for Michael last Christmas. He played with it I think twice. After I spent countless days looking for it and paying nearly $40 for it! grrr......
We got my dd the spelling turbo twist for xmas last year - she was 6 then. It was a set with the mind station (about $45.00) so we can upgrade lists all the time and it charts her progress - it hooks up through the internet. She loves it so much that she has asked for the math one this year (which was a much better price at TRU - 24.99). My mom picked up the fact blaster too for her.
It was defintely worth the money. Anything that is fun and helps them learn is a plus in my book.