I'm hoping that they will take the feedback and make sure that the paid guests consistently enter first. I'm not sure what happened on our day, but we headed over when they said we would, and we weren't first.
You can arrive whenever you want, but you are gambling a bit since you don't know how many people are in your group. We had a 12:05 and arrived at 12:20 because the kids wanted to ride the Luigi ride, which had a short wait for a change. If it had been a large group, we would have been waiting for snacks, drinks, and photos.