Like many have stated already, this event looks GREAT for certain situations, but not worth the money in others.
Back in January, I was vacationing elsewhere in Florida but was flying in and out of Orlando. I convinced my wife to leave our condo a day early so we could spend 1 day at one of the parks before flying home the next morning. Weighing all the options, we went with Universal instead of Disney because there was more we could get done in 1 day there. If this option was available back then, it would have been an absolute no-brainer to go to this event. The cost to attend wouldn't be that much higher than buying 1-day tickets.
If I were going during peak summer times and peak summer heat, and hadn't yet planned out my vacation, I'd probably be going also. I'd make sure to plan around it and either spend a day at the water parks or at the resort pool then head over at night. That sounds like an amazing day to me!
But in my current situation, it just doesn't make sense. We already planned out our trip months before this event was announced, which means our tickets have already been paid for, meaning this would be a true $149 add-on. We're going the first week of May where crowds will be manageable and the heat won't be oppressive (it'll be warm for sure, but not super humid yet). We are going to spend about a day and a half in MK. It'll be 4 adults, so there are plenty of rides to skip (Dumbo, AO, Carpets, Tea Cups, Regal Carousel). Which means 1.5 days will be PLENTY of time to do everything at least once. With the 4 of us being adults, there just isn't much of a re-ride factor. The idea of riding ANY ride in MK multiple times in a row does nothing for me. Ride everything once, feel the "magic", soak up the nostalgia, and be on our way. Splash Mountain is my favorite amusement park ride in any park I've ever been to, and I've been to about a dozen, but riding it over and over would cause the "magic" to wear off mighty fast. That's not so say that there's anything wrong with you if you'd love it by any means; it's just not for me!
So I can definitely see the appeal in certain situations, but it happens to not fit mine at the moment. Even still, the appeal of going to a dead MK with very few or no children running around is quite tempting! Ultimately though it doesn't make a ton of sense for me.
I can't understand why some people are so vehemently opposed to this. If it's not a fit for you, fine, but I don't understand why you don't want anyone else to have it as an option?