There is so much to do there, that unless you go for 14 days at a time - and who can afford that? - there will always be something you will miss. If you know this ahead of time and set a few goals that are reasonable, you will be OK. If you do nothing else, you have to decide beforehand what is important and concentrate on that. If winging it is important to you, then that is your "plan"!
I don't like to wander aimlessly, so I like to have some kind of plan. I have changed my ADR's twice for our upcoming October trip, but I think I'm all set now. I planned what parks we will go to in the mornings to avoid EMH's to maximize our "ride time", then made lunch ADR's if there was a restaurant I wanted to go to at that park. I built in rest time at the resort in the afternoon so we can go back out and stay out late without being wiped the next day. We have plans each night - everything from dinner shows and dinner reservations to "planning" to grab a counter service meal before SpectroMagic. Some things are flexible, like rest times and parades. The best part about planning and doing research is that I feel knowledgable. I KNOW that there is only one time we can see Spectro during our trip, so that day if we decide to go on rides instead of staking out a spot to watch it, at least we will be making a knowlegdable decision that we can live with. As far as going "commando", we have a list of MUST DO rides that we will try to do first thing in the am, but after that, we can wander until lunch or re-do the rides we liked best, or fastpass them while we eat lunch, etc.
I wish I could be more flexible, but I can't. If you go to WDW often or live close by, then you can afford to wander and see what strikes your fancy, or spend a day at the pool. If you can only afford to go once every few years, or if you are a first-timer, or going with one, you feel obligated to get the most out of your time there, considering how much $ you spent to get there and the fact that you have no idea when you might be able to come back.
One thing is for sure, you will definitely want to go back!
