I kept trying to figure out which Gilbert and Sullivan songs were the source material until I realized these were all original songs in the style of G&S. The play has many components inherent in early operettas: great voices, amazing melodies, great featured characters, surprise identities, and crowd pleasing production values.
What I didn't like
Some lyrics seemed a little rushed. Otherwise-perfect.
My overall impression
The sets, costumes, music, lyrics, and performances are all top notch. Gilbert and Sullivan would be proud to include this production in their canon.