They were right, for I was completely blown away by this Bergman masterpiece. 'Persona' is a powerhouse of emotions, and the acting is superb. Liv Ullmann's silence is extremely compelling, for her nonverbal communication conveys a whole lot more than any dialogue could relate! Bibi Andersson's performance is heart-wrenching at times, for her persistance and confusion draws the viewer into her corner like a spider caught in a web.
As far as Ingmar Bergman, I am now a dedicated fan of his films after viewing 'Persona.' There were a few bits during the opening montage that made me wince (beware!), but after seeing the entire film, I can understand why they were there. In addition, the visual look of some of the key scenes are among the most breathtaking I have ever seen in a film, such as the one where Liv almost floats into Bibi's room like a Nordic goddess.
Highly recommended for anyone with an interest in Ingmar Bergman, arthouse cinema or films about the psychology of relationships.