I just returned from my Thanksgiving "road trip." It surprised me that I'm now getting 3-4 mpg better highway mileage than before I swapped out the brakes. This was comparing my mileage for this trip to the ones I did all year long...up until I started hearing the strange noise. Guess It doesn't take much friction to significantly decrease your fuel mileage.
Guess the moral of the story is that if you see uneven wear on either the pads or the rotors, it's time to do a brake job. Hopefully it's something minor that doesn't require caliper replacement, but even that isn't too expensive if you do the job yourself.