We rented a nice villa for our '94 trip and are doing so again this trip. [Hampton Lakes, 4 bdrm, private pool for $525/wk tax incl.!!] We love having a house as opposed to living out of (and paying for) 2 hotel rooms for our family of 6.
As to driving...depending on how close your villa is it can be faster getting to the parks than using some of the WDW transportation. For example, on our last on-site stay we were in the cabins in FW and it would take about 45 mins. to get to a park using the buses!! Stop after stop after stop!! Ugh! In '94 we stayed in the Lindfield Estates and from driveway to theme park it was about 10-15 mins.!!
As to parking, if you get there early (recommended anyway) enough, you can get a parking spot close in. If not, they have (I assume they still do) shuttles that drop you off at the entrance. You can come and go and, as long as you save your parking ticket, you only pay for parking once each day. Tip: If we were going to the MK for the day but knew we were going to finish off the day with Illuninations, we would park at Epcot, take the monorail to MK, then the monorail back to Epcot in the evening for Illuminations. After the show, our car would be there in Epcot parking.