That trifecta of direction, acting and script in Hitchcock's film is nigh perfect, much like the murder it portays.
This film holds a weird kind of suspense. It's not the edge of your seat stuff or the oppressive terror of psychological thrillers. It is the suspense of intrigue. It is being taken along on a dialogue driven deconstruction of a murder that is so superb because of the meticulous filmmaking and superb line delivery. It is fascinating and engaging to keep guessing what will happen next and how our morally questionable protagonist will save himself from the net that is slowly closing around him.
The third act is perhaps a bit too drawn out, but then again I shouldn't complain as it allows us to spend a bit more time with one of the most beautiful women that ever lived.
This is, to me, one of Hitchcock's very best.