Opera is the last truly great Argento film and, although it’s final reel pull a few too many desperate twists, overall it ranks with his best work. The central image of the film is of Betty bound and gagged, with needles taped beneath her eyes to prevent her from blinking, thus forcing her to watch the killer’s twisted “homages” -- brutal acts of murder the equal of any in Argento’s repertoire. As a visualization of the director’s sado-masochistic relationship with his audience, it’s so intimate and honest it hurts.
(…) Although the story is giallo-esque, Argento uses the camera and his elliptical way with narrative to concoct scenes that feel as dreamily disassociated from reality as his supernatural-themed Suspiria and Inferno, with a recurring visit to a tightly coiled spiral staircase presaging sequences that float somewhere between flashback ans fantasy.
-- Steven Thrower om Opera i Horror -- The Definitive Guide to the Cinema of Fear (Marriot & Newman [red.], 2006)