Figured I would report back about this, based on our recent trip. Short summary - yes, this is a good show. Assuming you don't absolutely hate Frozen, it's worth taking the time to see.
We got there about 10 minutes ahead of time for the 6:30 show on a pretty busy day, and had OK seats. I would NOT get there right as the show is starting (the theater was full for us), but probably even just 5 minutes beforehand was still OK. No reason to get there super-early, though.
I didn't actually have much hope for this show - we went mainly since my 8 year old daughter is a fan of Frozen. Without giving the whole thing away, there's more to it than just the sing-along, and the overall show is really well done. My 14 year old daughter (who makes it a point to say that she does not like Frozen) was asking to skip it, but we told her no...she was smiling throughout almost the entire thing (although she didn't join in all the singing). The younger daughter loved it, and my wife and I had a really fun time, too. While we didn't have high expectations, I think we both felt this was the biggest "better than expected surprise" of our whole trip. And, the sing-along was the ideal way to put together a show based on this movie.
If you've seen Beauty and the Beast before but not this, I'd go for this one first. If it's just a one-or-the-other choice, I don't think you'll go wrong with either one. I'd put it ahead of the Voyage of the Little Mermaid (which we also enjoy, and is shorter), and even the Indiana Jones stunt show (which is very different, but kind of slow sometimes).