Great! This was my very first Sondheim show I lucked out on seeing on Broadway, in my very few trips to New York. (I also later got to see the orig.casts of Sweeney Todd and Into The Woods.)
The music of PO is quite beautiful. I think my favourite track (and staged number as they did it) was/is "Someone In A Tree". Then again, there's "Pretty Lady" and the simple but effective "Bowler Hat" (as it was staged then).
EDIT to add: Totally forgot about the beautiful haunting "There Is No Other Way", espcially when there is the 'outcome' from this number (SPOILER ALERT)..... where the hero's wife commits suicide. Very powerful number.
"Someone in a Tree" is one of my numbers. I'm singing as the old man. Sondheim has also gone on record as saying that is his favorite peice his ever written.
I'm also the French Admiral in "Please, Hello".