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.
YMMV: The Butterfly Effect
Darkness-Induced Audience Apathy: One of the major criticisms of the film was that it was so phenomenally depressing that by the end most of the audience was wishing they could spontaneously commit suicide too.
Family-Unfriendly Aesop: Depending on the ending, everything bad that happens to you and everyone you love can be traced back to simply being the kind of person they would love, or having been born in the first place.
Also in the Director's Cut ending, killing yourself is good if your family members and friends are better off for it.
Also counts as hideously painful Narm in some scenes. Sweet Jesus, the granola bar thing.
So Bad, It's Good: Some people consider the film this simply because Ashton Kutcher plays the main character. Whatever else can be said of him, he actually gives a fairly nuanced performance in this film.