I like guitar-USB stuff but I don't like the idea of being told by a computer program how I'm playing something.
Maybe for a beginner it would be good, but in that case, I'd want the beginner to learn properly, not like this.
I mean learning how to teach yourself is a valuable skill, and doing this won't help with that at all. I picture a legion of weekend guitarplayers all playing the exact same songs in the exact same way and looking at scores instead of listening. It might be a fun game, but it's not music.