We have always hopped, different parks in am as pm. We have never used our car or rented one, we rely on Disney transportation. I've seen the parking lots trying to empty and its just an endless stream of red taillights. There is no way we would want to be stuck in that mess to save, 10 minutes or more. And at the price of gas this summer, we're consolidating alot of not needed trips and errands around home.
When I go on vacation, we picked Disney since 1977 and over 34 visits, I like the convenience of not having to drive, find a parking spot and then fine the car again, plus the heat inside the car till the A/C catches up and all the roads in Disney to learn. Also now you have to contend with the traffic of a million other guests thinking they know where they are going in the dark and all the Disney buses. To me its not worth the aggravation , we sit back and let Disney chaffeur us around, its free and speedy.