Put us in the category of "always in August". Because there are penalties for taking our children out of school and because the holiday crowds would overwhelm us, August is now the only time we go.
We prefer the last week of August because the crowds are smaller than the rest of the summer and for some reason, the weather is not quite so rainy. Going in the heat of the summer forces you to slow down, have a sit-down lunch, take a break at the pool in the afternoon, a nap in the room and return to the parks in the evening.
Last Friday while I was waiting at the bus stop in 40 below zero weather in Boston, I kept trying to recall the heat of Orlando in August. It almost helped!
This past August we took friends with us who claim to hate the heat and worried about it in advance. They found the heat quite manageable because they followed the lead of their Tourguide MEM. Their only issue was blisters on their feet, but they did not listen to Tourguide MEM when she advised them on footwear to buy before the trip. Tevas are awesome!