I was wondering about this, too. I did some research on it a while back and decided against it due to the fact that if the fireworks get canceled, they don’t offer a refund. Since fireworks get canceled so often, and the fireworks display being featured right now as part of Mickey’s Mix Magic is not as immersive as the previous firework shows, we decided it wouldn’t be worth it for us. Even with the previous firework shows, it wasn’t possible to see the projections from the Skyline Lounge area. That said, there are still a lot of experiences we haven’t tried that were more of a priority for us during this trip. Once we have tried all the other things on our Disney bucket list, we may give this a whirl at some point just to see what it’s like.
Here is a link to a review of the experience that I read before making the decision not to try it this time:
https://wdwnt.com/2017/05/review-tomorrowland-skyline-lounge-experience-disneyland-total-waste-time/