Chrissee - they didn't charge us any more to pick up our car downtown and drop it at the airport.

Yes, definitely look into pick-up in town, and drop-off at Airport. If it's the same price or even a bit more expensive, it's still worth it as it saves a lot of trouble of getting back to the airport (the rental car companies at Logan are located outside of the airport, so you'll have to get to the airport then take the rental car shuttle bus to the actual location.)