We flew into Sanford last February and it worked out great. It took about 45 minutes to drive to WDW from there. We didn't have any problems with traffic, however we flew in about 11:00 P.M. and flew out at 7:30 A.M.
It is a nice small airport, which I like when travelling with my kids. We rented a car from Alamo. We got a fantastic rate - something like $139 for 9 days.
If you are looking at renting a car, the rental companies have pretty limited hours. However Alamo, while not technically open at the time of our arrival, did have a person at the counter. (We arrived about 11:00 P.M.). There were quite a few people picking up cars at this time. When we made our reservations, I couldn't find any other car rental companies that could accomodate our late arrival. With Alamo, I made our car reservation online, and then called them to let them know we would be a late arrival, so that they could make sure they had someone there. I also confirmed that morning for my own peace of mind.
Good Luck with your plans!