Jennifer, I've never done it, but families on my trips have shared their reviews with me. Basically, you nailed it when you said they range from magical to a crowded waste of time and money. Three or four years ago, the "magical" reviews would have outnumbered the "waste" reviews, but I think it tips the other way now because even low-crowd times get more and more crowded each year. Also, from what I've heard, Disney has increased the number of tickets they sell for this event, so it's gotten more crowded because of that. Usually the Halloween party gets better reviews, but even that event is getting more crowded and is getting fewer favorable reviews now.
All that said, I've had a few families who said their kids thought it was the highlight of their trip and well worth the extra money.
Hopefully others who've been recently will chime in.