I've seen the show twice, once in DC and once in NY, and I recall not being blown away by the score, in all likelihood because I was completely taken in by the amazing performance of Ben Platt. I remembered it as tuneful and catchy, but not particularly memorable. But a few weeks ago, I downloaded the OCR and my opinion has changed completely. I've become addicted to the music, and now realize that I, as have many, have completely underrated it. It has quickly become one of my favorite OCR listens. The story told by the music has helped me to understand the resounding success of this show.
I'm in the grandfather demographic, and the story and specifically the music and lyrics resonates even with me, and it completely resonates with kids and their parents in a very personal way no matter what their individual circumstances might be. It cuts across generations and socio economic status, and strikes deep emotional chords. I've seen criticisms here that some of the music is repetitive, but I disagree though perhaps technical musicians might hold to that opinion. But no matter. I think that this show will be around for a long, long time, even after the departure of the original cast.