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.
Cult Classic: The movie didn't perform very well financially, but it is almost universally loved among the show's original fans.
Crosses the Line Twice: included in the blooper reel is an extra take of the shot in which Mal orders his crew to mask their ship as a Reaver's. The original scene is very nearly a Kick the Dog scene, but the moment Mal's improvised orders change from the script is the moment that he takes the line and guts it with a screwdriver.
"Put Book front and center; he's our friend, we should honor him. Kaylee, find that kid who's taking a dirt-nap with baby Jesus — we need a hood ornament. Jayne! Try not to steal too much of their shit!"
Moral Event Horizon: The Operative's destruction/massacre of anywhere/anyone Serenity might go to for help.
Saved by the Fans: The internet petition drive started by fans ultimately led to Universal picking up the movie.
They Changed It, Now It Sucks: Some fans of Firefly were not pleased that the "space western" elements from the TV show were dropped in favor of a more traditional sci-fi feel. This is ignoring the fact that many entire episodes of Firefly were largely sci-fi and had little "western" to themnote "Bushwhacked," "Out of Gas," "Ariel," "War Stories," "The Message," "Objects in Space" and the entire intro sequence of the movie was as pure "space western" as you could get.
Uncanny Valley: This is where the lovedoll designers of the future are situated.