I myself am one of those who very much appreciate the film, for reasons I'll get into later. Vertigo's story is one that can be traced back to Gothic roots, whose tales were characterized by Dopplegangers and unattainable love that culminated in death. James Stewart's character is tormented by double images of the woman he loved, so there is a certain connection. Also, that premise is simple enough, yet passing the halfway point is usually when the film loses people's sympathy for the character of Scotty. After his trauma from the death of Madeline causes him to fully reject the affection of Midge, Scotty descends into an obsessive realm that is peppered with images connected to the deceased woman. A protagonist obsessed with images rarely ever turns out well in the end. Just look at the character of Humbert Humbert in Lolita (1962), played superbly by James Mason. He is consumed with the image of the young Lolita but only the image, to him, nothing else matters. He cannot accept the wilted flower that she becomes later in the film, yet he could do nothing to preserve her as such.
The same goes for Scotty, he pines for Madeline in the same way, only he goes a step further, forcing her image onto Judy. Now, when I said earlier that I am able to appreciate the film more than most, I'm not talking on a cinematic level, as in editing, cinematography, etc. I am referring to the fact that I sympathize with Scotty's plight, not his actions. It is entirely human to become obsessed, for some more than others it has occurred a few times. It would be folly to say that it had never happened to me. Because of those experiences I feel a very uneasy kinship with Scotty when he passes a woman who reminds him exactly of Madeline and he can't help but stare. Here Hitchcock is reaching into a niche part of the audience, but also into a part of himself that was very much evident from his career. In fact, there has been made a recent TV movie that capitalizes on his most sensationalized muse. However, for everyone who has come out of these obsessions, they know that it is something destructive, the obsession exists solely out of the desire for the unattainable. Yet, there is still that nagging feeling of "what if" that lurks beneath, the feeling of wanting that person or image as their own. Hitchcock certainly has that feeling, being the quite jealous man that he was. It is known that he was heartbroken when Ingrid Bergman quit starring in his films to marry the Italian director, Roberto Rosselini. No longer would he be able to capture her image on the celluloid of his mastery. As Scotty reconstructs Madeline through Judy, there is the sick sense of fulfillment, that reaches its climax when they kiss and Bernard Herrmann's music reaches a Liebestodian peak.
Hitchcock is wise enough, however, to reveal what actually happens to an image of obsession. It is lost, again. Not everyone has had the same experience of being consumed with a person and this is why some people are repulsed by the film and Scotty's treatment of Judy/Madeline. They don't understand how someone could come to do this sort of thing. Now I'm not saying that if you haven't had a similar experience, you won't enjoy Vertigo, on the contrary, there is much to enjoy from it from the gorgeous look of it, to the intricate plot. However, to grasp the full director's intent and purpose, I believe that you must have had to experience your own personal "Vertigo".