Mark Meatto strikes an effective balance between focusing on ambitious musicianship and stealing sidelong glances at internecine tensions… [offering] an intimately up-close look at the formation of Punch Brothers, a progressive bluegrass ensemble begun by mandolinist Chris Thile after the break-up of the Grammy-winning acoustic trio Nickel Creek… [The film leads up] to a triumphant New York performance that is the pic’s musical centerpiece.—Variety