This reminded me of Randy Pausch's last lecture (if you haven't had a chance to watch it, I highly recommend it - http://www.youtube.com/watch?v=ji5_MqicxSo). Teaching kids is all about headfakes* - you are't encouraging them to play soccer so they can go and play in the World Cup, but rather so they have a fun context to learn about things like hard work, practice, and teamwork. Analogously, I think this personalized Harry Potter app just teaches his daughter that learning doesn't always have to feel like work, not specifically that she should spend all day trying to get praises from Hermoine and British men answering math problems.
* Disclaimer: I don't have kids and know little to nothing about raising or educating kids.