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.
Evil Is Sexy: Der Tod's evilness is as much up for debate as his sexiness.
Fridge Brilliance: Some parts of the musical really aren't historically correct, blatantly biased even. It all makes sense if you think of this: Lucheni is the narrator, and everything is seen through his eyes!
Genius Bonus: While it's definitely not necessary to enjoy and understand the show, knowledge of Heinrich Heine's poems helps you understand a lot of der Tod's lines. Also, many lines said by Elisabeth, Franz Joseph and other Historical Domain Characters are based on things they said or wrote in reality.
Ho Yay: Der Tod's duet with Rudolf, "Die Schatten werden länger" ("The Shadows Grow Longer"), is basically made of this.
Also, quite often there's something going on between Lucheni and der Tod.
Iron Woobie: Franz Josef gets this big time. After what happened to him in real life during and after his time with Sisi, could you really blame him?
Rudolf too. Poor guy exists only to be tormented by his grandmother, and then ignored completely by his mother. Who then turns him away the one time he asks for her help. Is it any wonder he is Driven to Suicide?
"Ich flieh, wenn ich fremde Augen spür,/ denn ich gehör' nur mir".
"Majestät, der Krimkrieg droht sich ernsthaft auszuweiten. / Dass wir Russland diesmal beistehen, ist nicht zu vermeiden." (This one is made worse by the fact that most actors tend to overpronounce the different consonants in the "rhyming" words, making the flawed rhyme even more obvious.)
"Nichts ist schlimmer, als zu wissen, / wie das Unheil sich entwickelt, / und in Ohnmacht zusehen müssen."
Tear Jerker: Oh god, where do we start? Most characters die (and since they're all historical figures, it's safe to say that all of them died), there are tons of child-parent-conflicts, tons of dark looks at society, future etc. Really, it'd probably be easier to write down the scenes that aren't heartbreaking.
Woolseyism: The Hungarian production gives considerable attention to the impact Elisabeth had on Hungary herself compared to the Viennese versions. The Japanese productions adopted this interpretation too, probably because it gives the actor (or actress) playing adult Rudolf much more to do.