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.
Broken Base: When Aaron Tveit, the original Gabe, was replaced by Kyle Dean Massey, the fanbase became divided between who was a fan of the show and who was a fan of the cast. And don't even get them started on Alice Ripley vs. Jessica Phillips vs. Marin Mazzie.
Crowning Music of Awesome: A lot of it, including "You Don't Know"/"I Am the One," "I'm Alive," "Make Up Your Mind"/"Catch Me I'm Falling", and "Light".
Ensemble Darkhorse: Gabe and Natalie, while extremely important, aren't the leads—that honor goes to Dan and Diana. Not that the fandom would let you guess that. Natalie, in particular, gets a lot of love and sympathy, since the show's (massive) teenage fandom can relate to her desire to be appreciated and loved, as well as her struggles to be the best.
Informed Ability: We are told Natalie is a genius, yet she is shown struggling with schoolwork and piano, which people in real life have been able to manage without any problem. Although this may be a result of her having to deal with a dysfunctional family, in any case, as far as we can tell, she doesn't seem to have any abilities that seem Yale-worthy.
Tear Jerker: "He's Not Here", "A Light In the Dark", and pretty much the whole last half hour of the show.
The Woobie: Every member of the family for their own reasons.
Natalie because she is neglected by her mother and always coming in second best to a brother that isn’t even alive.
Dan is trying to keep together a dysfunctional family while trying to keep a façade up of everything being fine.
"Now I'm strolling right beside her as the blackhole opens wide, mine is just a slower suicide.
Diana is the biggest and most prominent in the show. She has to deal with a mental illness, what is either a sadistic and domineering projection of her subconscious, or an angry spirit fearing being forgotten, who looks like the son she lost, and to top it all off, her family is starting to crack because of her.
Gabe. If you really believe his presence is there. He doesn’t want to be forgotten by a family he barely knew.