Well it feels like both a radically different show (because of the book) and the same show (because there is essentially only one new song). The book to act two does away with the fashion show and everything Arachne sang except Turn Off the Dark. There is a cohesive plot that makes sense, is linear and easy to follow.
The new song is for the Green Goblin called Freak Like Me. It was unfortunately weird and kind of cringeworthy. Much of the score is rearranged, re-orchestrated and sung by different people. Still this is not enough to mask the lack of theatricality in the music.
The show, imo, has certainly become respectable and decent, although never fully engaging or brilliant theater. I could go on for paragraphs about all the changes to the book, but could also try to answer any questions.
Marie: Don't be in such a hurry about that pretty little chippy in Frisco.
Tony: Eh, she's a no chip!