I agree that it depends on the child. We are scheduled for a late-August trip, and our 5 year old will NOT be using a stroller. She has not been in a stroller since she was 3 1/2 (maybe 4).
Personally, I think part of it is a balance between the child's needs and what the parks are like when you will be there. When it is REALLY crowded, trying to push a stroller around is a nightmare, and I truly feel bad about crushing ankles as I am trying to push a stroller. However, even at Disney, there are people who get downright nasty to people with strollers.
I, personally, am glad it is one less thing we need to deal with on this trip. Plus, our little one, without a stroller, helps pace us. When she complains she is tired, we all take a break. Otherwise, with a stroller, we would just GO GO GO, and then our 9 year old suffers.
Anyway, always a responsible parent's decision. Just weigh all the options and the +'s and -'s before you decide...