For what it's worth, we stayed there June 2018 for a conference for my husband. We did a split stay, both on Disney property (before/after conference) and at Marriott during the conference My daughter and I went to Epcot during one day of the conference, and the Crayola Experience another (she was 7). We loved the resort! Upon seeing my daughter, the check in employee automatically told my DH "You need a fireworks view" and did it for free. We could see the Disney fireworks from our balcony which was fun. My daughter loved exploring the resort and riding in the clear elevator even though we did not stay in that building. We liked their nighttime laser show, and their pool area was amazing. We also used their transportation to/from Disney for our day at Epcot. My husband actually had used it a day previously and was able to give us a walk through the night before, so that next morning we knew exactly where to go to load the bus. It is more restricted but it ran once every hour and we did fine with it. The only frustration I had was it drops off at all four parks and of course ours happened to be the last one!
On the flip side, his employer did not give an option to stay anywhere, or I probably would have dabbled with onsite for convenience sake. But the World Center has tons to do and we really enjoyed our stay.