Flight, check. Hotel room, check. Rental car, check? While it's usually cheaper than constant cab rides, especially for long distances, I like to at least look into local public transportation alternatives before budgeting for a vehicle.
I know it depends on the location and the trip's purpose, but I've got friends that wouldn't dream of visiting any location without getting a car, including NYC where parking often costs as much as the rental rate itself! Members of sharing programs like ZipCar can still grab a vehicle for minitrips in available areas, so how automatic is auto booking for you?