I performed in this musical during my senior year of high school. It was easily one of the coolest things I've had the opportunity to be a part of- my high school was the first ever nonprofessional group to get the rights to do Phantom, and the producers from New York came to our show. We even got the chandelier driven in from Las Vegas and wired with hydraulics.
The music is very difficult. Lloyd Webber is thought to have written it vertically, meaning each beat of the measure got certain notes, but usually without regard to which voice part sang which note in the previous beat. Each note, when done well, sounds great. But each part on its own can sound ridiculous, and we often found ourselves all over the staff. The melody doesn't belong to any one vocal part, it switches between all eight.