I've done EMM at MK (twice) and HS (once) and it was 100% worth it every time. I am hoping take my sister to do EMM at MK again in March.
Being in Fantasyland when it is virtually empty is a special experience. Riding Peter Pan & 7 Dwarves Mine Train over and over again with zero is something that could never happen during normal park hours. Usually I would end up using a FP+ for both of those rides, so doing EMM saves me two fast passes for other headliner attractions later in the day. Additionally, while everyone rushes to Fantasyland at rope drop, I can be somewhere else in the park when it opens and potentially ride another one or two attractions that I might have used FP+ for. Getting a handful of those headliners/popular attractions out of the way early on puts me ahead of the game (and a few steps ahead of the crowds) for my ENTIRE day at Magic Kingdom.
And the buffet is pretty good, too!
The EMMs are some of the best $$ I've spent at Disney. Yes it's expensive and maybe it's not worth it for everyone (if I had a large family I would probably skip it tbh, as it adds up quickly!) but for me it's been a magical way to maximize my time in the parks.