Welcome to the DIS and the Transportation Board!
First off, you will hear way more horror stories than good ones. It is the nature of the Internet, people love to complain.
Personally, I always use the buses and enjoy doing so. You will get opinions on both sides, but I enjoy the buses, monorail, and boats. Even when we rent a car, we still use Disney transport to get us around property...... riding the buses, monorail, and transport allows me to soak in the entire trip instead of worrying about street signs, cooling the car, parking, etc.....
The only crowded times are near park opening and closing. The buses run way below capacity during the middle of the day.
Essentially, it is up to you. If you rent a car, still give the buses a try, you may like them. If you don't, then you still have the car.
Duds