I got a pretty good rate when I bought my car (4.75%), but my finance guy still advised to pay the thing off as quickly as possible.
While conventional wisdom suggests not tying up your money in a depreciating asset, by keeping the loan open, any profit you make you make is offset by the money you are loosing on the loan.
This is a personal decision, so do what feels right. If you have financial advisor that you trust discuss it with him. We're not exactly financial experts here - we bought a car for $40k+ when you buy perfectly good transportation for less than half that