The part that I found interesting was the ability to show the overtones and harmonics. If you know that player xxx that you are trying to emulate has a certain sound profile, then you can try to shape and match that sound with some meaningful visual cues. Or, if you are having trouble hitting the third or fourth partial in an overtone series, working to bring that out while playing the fundamental might trigger that "aha" moment.
I'm not sure how well it works, but I am intrigued. It does sound like having a good quality USB mic is a must.