I think one of the important points to remember here is that, although this is a Florida forum, it does tend to attract villa owners and renters more than resort and hotel guests. This alone does make the use of a hire car essential in my eyes.

I know people who have stayed in the Disney hotels everytime they have been and haven't hired a car for any of their trips (one couple are in the vacation club and go twice a year for the last 5 years at least. However, you try having a conversation with them about Old Town, Clearwater, Boggy Creek etc. Ask them which places they go to eat at in the evenings. The answer is always the same - hotel/park.

Another family we know actually paid for Universal tickets but then never went because it was too much hassle using the Disney transport - that wouldn't have been the case if they had a car.
It all comes down to what you want out of your holiday, and if you are happy to spend your time being ferried around on full to bursting transport - after waiting god knows how long to get on it in the first place (but we're British so that shouldn't be a problem). Also if you don't mind eating in the same places all the time and not experiencing the REAL taste of Florida, and if all you want to see in Florida is what Mickey and friends have to offer then I'm sure you will have a great time.

On the other hand however if you are a bit more adventurous, want to spread your wings and see beyond Disney/Universal and get more out of your holiday than eating, sleeping and playing in the vacinity of the hotel then a car is a must.

Kenny