I go back and forth on that. For many years we've used our rental car. However, we won't have one next year, and I'm fine with that. I think it does save time and does cut some of the standing-around-and-waiting out of a trip to use the rental car (EXCEPT between MK resorts and MK, and Epcot resorts and Epcot or D-MGM), but not so much to make a big difference.