we went june 4-11th this past june. we had only gone in the off season (jan, sept, mid nov) before that trip. wow, what a shock the crowds were to us! but we knew it would be so we planned planned planned. up early and to the ee park, out of the park after lunch and back to the hotel pool. we didn't go back to a park until after dinner. using fastpass was key.
the long hours are great and we finally went to a waterpark! the weather was HOT, mid 90's every day and it rained. not the brief shower you hear about but torrential downpours lasting for hours every night (not that we let that stop us!)
it was a great trip but we'll stick to the off season until the kids are school age.