In the past, we have always ridden the buses. This past trip, though, we wanted to hit as much as possible, and the buses just weren't cooperating so we rented a car and found life much more simple.
I do not drive to MK, nor do I like to drive if I know i will be leaving at closing time, with all the traffic. We did EMH at epcot last week when it was quite chilly, and we left when the park closed at midnight. We were one of only three cars in our lot area (but we did get to see all the buses lining up for the 1/2 marathon, which was really cool).