Brutal. The first half was violent, but no worse than a lot of other movies. It had elements of revenge, home invasion, and a pretty scary human demon creature. A couple twists during this half kept these less-than-original concepts fresh. The second half, however, truly did live up to the hype. Gutwrenching and hard to watch. However, unlike other torture-themed outings like Hostel and Saw, what really sets this movie apart is how it gets you thinking. In the end, we learn that agony is relative, and the viewer finds relief when the pain becomes so fierce it's transcended. Not for the faint of heart, and not recommended for most viewers.
I've read that this movie about Hitchcock's obsessive relationship with The Birds and Marnie leading actress Tippi Hedren is historically inaccurate, or at least exaggerated. Given that some of the basis for the story comes from Hedren's personal accounts, I have to believe that it's at least loosely rooted in fact. However, "Alfie"'s spiral into near-insanity as portrayed in the movie's final chapter, to me, bordered on caricature, and is hard to buy into. Given that the rest of the film, save for a few good creepy moments -- Hitchcock throwing himself on her during a limo ride, his (implied) intentional shattering of the phone booth glass while she was inside, his 5-day marathon assault on her with real birds in the attic scene -- was actually pretty uneventful and not particularly tense, it's hard to give this movie much of a recommendation. It was interesting from a historical perspective, but average as a drama or thriller. As a Hitchcock fan, I may have enjoyed it more than I expect most would, but that's not saying a lot.