These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Sondheim and Furth have stated that the reason Bobby hasn't been able to settle down is not because he's a closeted gay man, but for a while there was talk of a rewritten version where Bobby is openly gay and struggling to commit to one man.
Awesome Music - It's Sondheim, so there's quite an abundance, but Being Alive, The Ladies Who Lunch, Marry Me a Little, and Another Hundred People are all showstopping pieces.
Bobby... Bobby... Bobby baby... Bobby bubbi... Robby... Robert darling...
What Would We Do Without You, You Could Drive a Person Crazy, and The Little Things You Do Together all count, as well.
Ensemble Darkhorse - Joanne seems to be very popular. Having been originated by Elaine Stritch and since then played by the likes of Patti LuPone helps, in addition to the fact that she is a Deadpan Snarker with a great many hilarious lines, and her song The Ladies Who Lunch is one of the best known numbers from the show, and can easily bring down the house.
Christina Hendricks' portrayal of April in the 2011 concert version was extremely well received as well, with her monologue actually stopping the show as the audience laughed and cheered.
Funny Moments - In Poor Baby, Bobby is shown having sex with April while all of his married female friends comment that he ought to have a woman, but not someone like the one he's with right now. They list the things they each find wrong with her, such as that she's "dumb", "tacky", "vulgar", etc. Joanne's complaint? She's "tall enough to be your mother".
Genius Bonus - Joanne comments that smoking is "the best", saying that it's "better than Librium". Librium was a precursor to Valium, a sedative/muscle relaxant/anti-convulsant/anti-anxiety drug, mostly prescribed short term for anxiety. You know what else it's prescribed for? Acute alcohol withdrawal.
Signature Song - Being Alive and The Ladies Who Lunch, and to a lesser extent Side By Side By Side and Another Hundred People.