We went in December and the wifi at AKV, AKL and the parks worked great. The Sunday we were in the resort, I was even able to stream the Houston Texans game so I am sure i stole some of the shared bandwidth from others connecting to the same access point. So, i appologize for your 10 year old not being able to watch Justin Bieber videos on Youtube.
Usage will be determined by how many people are connected to a specific access point (usually time of day dictates this), what type of devices and what they are doing while connected to that specific access point. That is why you see so many differrent experiences. This happens everywhere when large number of people are connecting to wifi. Similar to when you are at a football game and phone service stinks because so many people in one area are trying to use a limited amount of capacity.