Gut feeling, mostly, at this stage. I haven't asked how sales are doing or anything like that. But I am watching the advertisements and announcements roll out, and if I put myself in the shoes of an average guest who doesn't know anything about this event other than what Universal's publicly said, it sounds like a cosplay event with some special characters and food.
I think they need to do a better job explaining the scope of some of these "experiences," even if it means releasing some renders or concept art. I don't think people understand they're going to get to visit a Star Trek bridge with live actors or encounter a giant, physical dragon.
I suspect advertising this will get easier after the initial week, as they'll have publicity footage they can push at that point. But this event only runs for a month or so...