Incredible film, well worth the wait, but what a pity we did have to wait so long.
Regarding the Demon debate, whether or not it should have been shown, Tony Earnshaw's book on the making of the film, Beating the Devil, covers the matter pretty well, including some quotes from Tourneur and other crew members that seem to be contradictory; that is, in most places he seems adamant that the demon did not appear by his design, but in one or two others it seems that he was not just aware, but also active in placing it within the film. Personally, I suspect that the truth can be found by watching the film itself. There are two elements to the Demon special effect: the long shot, which is absolutely stunning, particularly given the low budget on which it was achieved; the other is a rather pathetic man in a monster suit, which appears very briefly, and could be seen as justification of Tourneur's repugnance for the appearance of the Demon. I have no doubt it is only these few dozen frames featuring the rubber clad SFX man that could have caused the director's consternation. The shame of it is that they could easily have been left out without affecting the film in anything but a positive manner.
MAKE NO MISTAKE - The appearance of the Demon is incredible, adding to and complimenting the film, and ultimately being the thing that stamps the film in the mind. Without it, the film would have still been great, but I suspect it would not have fascinated so many minds for so many years. Any pseudo intellectual babble about it spoiling the film in any way is ill conceived. It is only a few frames that do the damage, not the presence of the demon itself, and they are not enough to take away from the over all effect.
In my opinion, the appearance of the Demon is one of the most brilliant realisations of a film monster in any movie of any time, and one of the most striking scenes in movies full stop.
Tony Earnshaw's book is an excellent companion to the film, though I suggest watching it before reading the book, and then watching again.
But whatever happens, make sure you do watch it!