I wouldn't run, but I'd pay it off on your next lunch break.
I had exactly the same thought process about my mortgage, which I paid off over the last year or two. I think the logic is sound.
Two things to point out:
1. On the bad side, you might be writing off some of the mortgage interest expense on your taxes. If you are, then the 4.75% isn't quite as good as 4.75% because after you pay off the mortgage your taxes will go up somewhat. But from what you've said, you may already be at the standard deduction so this wouldn't apply.
2. On the good side, the 4.75% is guaranteed risk free, which is obviously better than any 3 year bond out there on a risk-adjusted basis.
I'd make sure I had a comfortable emergency fund first, which you probably do.
Good luck!