I would absolutely love to walk away from my house right now, it would save $35-45,000 at least. Probably wouldn't ethically anyway, and I'm in a state where they would come after me for the money anyway so it's not an option... :)
That has nothing to do with your great catch at finding a rate at less than half you are paying now for a huge chunk of money! Being able to pay in advance is actually kind of nice, that way once you have paid forward a bit, you can always not pay if some hardship comes up. On the other hand, it might be that you will pay full interest instead of paying less interest as you pay it off quickly. So if you took the loan for $60,000, paid off $20,000 a month later, are you paying interest on the equivalent of $40,000? Or still paying interest as if it was just under $60,000? It's possible they have calculated the interest over the course of the loan and even if you pay ahead you aren't saving interest on the amount you have paid off. Something to consider if you hope to pay it off quickly.