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.
Growing the Beard: Hugh Jackman did so literally and figuratively with this film. Before The Fountain, he was still largely known for his roles in crowd-pleasing action movies (X-Men, Swordfish, Van Helsing, etc.), and few people had any reason to see him as anything more than a generic "bad boy" action hero. With his role as Tommy, he showed that he was willing to work on more experimental films that weren't guaranteed blockbusters, and he got to showcase his impressive acting range for one of the first times in his career.
He Really Can Act: Jackman, who plays three different characters in the film and does so amazingly well. In fact he spent hours with Aronofsky working on the physicality for each of the three roles. Tomas the id, with a very aggressive walk, coming straight from the pelvis. Tom the superego, incredibly emotional and light. Tommy the ego, very cerebral and driven, focused.
Narm: Some people found it absurd how the flowers explode rapidly on Tomas's body when he drinks from the sticky white sap of the Tree of Life.
Vindicated by History: Even though this movie was largely ignored by the awards circuit (see Award Snub above), audiences in more recent years have been a bit more willing to at least recognize its ambitions, largely because the one-two punch of The Wrestler and Black Swan helped make Darren Aronofsky an Academy darling once again, proving that Requiem for a Dream wasn't a fluke. It's still considered one of his weaker films, mind, but it's at least regarded as a crucial entry in the filmography of one of the more notable directors in the business today.