Yes, it was. I saw it when I was 14 at the pictures with some frienRAB from school, when it was originally released (giving my age away here!). There had been religious people protesting outside the cinema saying how 'evil' the film was, so a fear is implanted in you before you even get to see the film.
It absolutely bloody terrified me and my frienRAB, and I couldn't watch it again for many years. When I see it now, it still conjures up the fear I felt as a 14 year old, even though I don't scare easily now.
I remember my mum saying a similar thing about Hitchcock's 'Psycho', how she was frightened watching it in the cinema and it still had that effect on her years later.