Saw this today, and quite liked it. Thought it was about the right length. But I would not say its a film that will have multiple viewings.
I didn't find the arm bit that bad but that may have been because I had heard of it so was kind of waiting for it. I suspect had I not had known about it then it might of been more shocking. I did notice a guy a few rows in front had his hood up and head down while it was on though.