I feel ill-equipped to review the movie, because I don't want my lack of professional movie-reviewing skills to detract from how great it is. I'll do my best. If your sense of humor is like mine (favorite comedians: Paul F Tompkins, Maria Bamford, Jim Gaffigan, John Mulaney, Al Madrigal . . .), don't miss this real treat of a movie.
Taste in comedy is of course, very subjective. I would say use whether or not you liked Napoleon Dynamite as a baseline for whether you will like this movie. You either like cilantro or you don't. You either like subtly silly movies that are quirky without being creepy, or you don't. This is an underdog becomes the hero story, played out in the world of people who are in the margins of our culture: homeschoolers, sci-fi fans, dwellers of geodesic dome houses.
In this one, a homeschooled, amateur novelist teenager, Benjamin, played by Michael Angarano (Young William in "Almost Famous", young Red Pollard in "Seabiscuit") attends a teen science-fiction writers' conference, led by his hero, hit sci-fi author, Chevalier (Jemaine Clement of Flight of the Conchords, Men in Black III, etc.). I don't want to say, "When Chevalier plagiarizes Benjamin's novel, hilarity ensues", because the hilarity begins in the first two minutes.
Like a Robert Altman movie, that gets you into a world you've only ever given a cursory glance from the outside, Gentleman Broncos gives you a real taste of the world of homeschoolers: the doting, struggling, sometimes oddball parents, the usually great relationship between homeschooling parents and their children, the confidence, misplaced or not, homeschooled kids have that they can do what they aspire to do. While not typical, there are certain great little details that homeschoolers and readers of Mother Earth News, will recognize. The plot, the dialogue, the action aside, these sweet little tidbits make watching this movie like eating a really great tira misu.
All the performances, from every actor, are just perfect, as is the casting. However, I would be remiss if I didn't mention the really standout performance from Sam Rockwell, who plays the protagonist of Benjamin's novel in the Benjamin's and Chevalier's duelling versions of it. When is Sam Rockwell going to get an Oscar, already?