I don't get it. Why rent a car when staying on Disney property. One of the many perks of staying on property is using the bus service. We've always stayed at values but once and the bus rides aren't that long...goes by pretty fast. It's free to park if staying on property.....but I hear it's a PITA when arriving/leaving the parks, plus you have to take a trolley or something after you've parked to the park entrance. We've even driven to Disney 3 times and our van stayed in the same spot the whole time. The bus service is part of the resort experience and I love it.
The first trip I took with my DS in 2008, I didn't rent a car. We stayed at PoP and relied solely on the busses. My touring plan however, was very simple. We go to one park a day. We never went offsite to Universal or other attractions. We didn't do any mini golf. Our meals were either at the park we were in or at one of the monorail resorts. We had an amazing trip. We had no need for a car. Great time. We did this on subsequent trips. The one issue that we did have is we went to the HDDR at Fort Wilderness. Getting there was pretty simple b/c we just took the boat from MK. However, getting back to the hotel was a nightmare. AFter the show ended they had busses. We had to wait at least 45 minutes for the bus to leave. Then it stopped at at least 4 other hotels before going back to PoP. My son was just dead weight at this point. (When we did this again years later, having a car was amazing)
A few trips later when my DS was older, I realized there was more I wanted to do. My son having read all the Harry Potter books, had to go to Universal (ok..I wanted to go to. Plus Sitting at the bar at Moe's in Springfield is just all sorts of awesome). A few months prior to this trip we were visiting family in Atlanta and went to the Aquarium and saw the dolphin show where the trainers were in the water with the dolphins. My son tells me that he wants to do that. A quick google search later and Discovery Cove had to be done! So we had a trip where we were going to spend at least 3 days offsite.
Add to the fact that my DS and I are both now foodies, we wanted to go to the other resorts to try the restaurants. To take a bus from Pop to MK, spend a day at the park, then a bus to AKL, to then either have to take a cab back or trek back to a park to get a PoP bus, did not sound at all appealing.
I then went and used a taxi calculator to figure out how much including tips it would cost to go from Pop to my other destinations. It was without a doubt cheaper to rent a car.
I think the car/no car issue is all about what you plan to do with it. If you just plan on waking up, going to a park and then going back to the hotel, then you have no reason to need a car. However, if your plan includes going off site or bouncing around. Then you do.