This looks really good and it is a great idea. But there's a problem. It would be way more expensive than guitar hero or rockband since it uses a real guitar.
I agree with ngfan14, it's going to be a lot more expensive and many people cannot play it, it's probably more of a game meant for people who actually play the guitar but can't play guitar hero or rock band :O
and if it teaches you then cool, it could be worth the money