Our first trip home to SSR was after Christmas 2006 for five nights, and we really enjoyed using ME. However, my wife and daughter wanted to go to the Premium Outlets and other excursions. Not for me! Why go shopping in Florida??
So, there is a Alamo/National car rental place just outside of MK; you can find their number in the Disney info found in your room. I reserved Alamo for about $59 a day (National was about 10-15 more for some reason), and scheduled a pickup time. They picked me up right on time at SSR checkin, took about 10-15 minutes to get there, and about 10 minutes to checkin for the car. Make sure you have a credit card with you; you can avoid the regular checkin and go straight to one of two automated machines. If you are a non-US citizen, I think you have to use the regular line, and it looked slow!
I used the car for about two days, returned it to the MK area location, and had to wait about 15-20 minutes for the shuttle bus to pick me up. We will probably do this again, but will reserve via internet ahead of time. The 59 a day was pretty high, but not bad considering we did no advance planning.
Next time we would use ME to arrive by mid-afternoon, and arrange for a shuttle to pick us up at the resort that day. Use the car for grocery shopping on the way back, and other shopping for maybe two days total. Then return and use the Disney busses after that. Sure we can get a much cheaper price this way.