We flew into Sanford in November for the first time - while we did miss the variety of shops, etc. on the return trip after we checked in for our flight, it was certainly quick, and easy on the pocketbook!
We rented a van from National - right onsite - with no trouble at all, and the airport is so small that baggage claims, etc. are quick and easy.
I didn't find the drive to be a problem at all - but we were travelling on Sunday - when I-4 is not congested. We drove up Lake Mary Boulevard about 8 miles - stopped off at the store to pick up some treats and adult beverages at a reasonable price - then hopped on I-4 West for a straight shot to Disney!
I would definitely fly into this airport as well, if the price were right, since we always rent a car. Just a little something to consider, however, the rental car agencies close around 5 pm.