I can see both sides of the go/don't go debate. For what it is worth, I've a great many WDW visits under my belt, but just 2 WDW water park visits, both fairly recent. Truly, I bought the tickets years ago!
I like the comment about WDW pools! They are super! We love them, and they are all very fun. Many offsite pools are equally fun! Some trips, it is hard to squeeze in the time. Other trips, the weather doesn't cooperate. Most trips a fun pool is plenty!
To answer the question in your title: our first visit was high summer. We went 11am-closing. Lines, but not too bad. We did everything. theming is more fun than other water parks, but still just a water park. IMO, the WDW theme parks are more unique.
Our 2nd visit was just two hours. It was the only day we could go, and an unseasonably warm winter day. Our only real wait was Crush and Gusher, we covered most the rides at TL, except the shark reef. (takes a while + chilly water)
We found it best to minimize what we brought! If you don't bring anything, then you don't need to hunt for your stuff later. We didn't need towels, though full confession- we drove. We only took the car key (minus the FOB) zipped in a waterproof swimsuit pocket. We were mostly dry before we reached the car. WDW sells lockers, but there's a wait. You also lose time hunting for your spot.
Wear water shoes! (water slippers!) You feet will thank you! Barefoot is a bit icky. Shoes also = endurance! For us, concrete (all day) and bare feet = sore feet. We paid the price for the rest of the week! Try (a place like) Kmart for under $10 a pair. Well worth the $! Happy feet= happy WDW!
