I have 4 boys. An 11 yr old, 9 year old and 4 year old twins. We stayed at ASMusic last year and loved it. We stayed here in June. We are staying here again this year. Our experiences with busses are not the same as others have said.
In the morning we didn't have to share a bus with other AS resorts, but the busses were always packed with as many people possible standing. This doesn't bother us at all, and we don't mind.
In the afternoon when we left our resort we didn't stop at other AS resorts, but when leaving a park in the afternoon our bus always stopped at the other AS resorts to drop others off.
In the evening it was the same. When we left our resort the bus was full and just took us to whatever park we were going to. When we left a park in the evening it always stopped at other AS resorts.
When we were going to DTD, we usually stopped at a water park first (not sure which one) then on to DTD. When leaving DTD, we stopped at other AS resorts.
It seems like the "sharing" of the bus for us was mainly when we were leaving parks and the bus was making the rounds dropping others off. Sharing a bus is not that big of a deal to us. There were so many times last year that my 4 year old twins took short naps while we were dropping off at other resorts that I was usually glad for the extra time on the bus. I relaxed for a little bit while they slept. There were times in the evening that they fell asleep on the bus, we carried them to the room, and got them ready for bed, and they never woke up.