This cult film is generally considered the first time David Cronenberg connected with a larger audience ... his next film was Videodrome. I'm not a big fan of Cronenberg, although I thought A History of Violence was terrific. So while I can appreciate the importance of Scanners as an early sign from a respected film maker, it didn't do much for me.
The main problem was the acting (in fairness, some people thought the acting was fine). More specifically, the acting when scanners used their powers was ludicrous. The actors were forced to overact with their facial muscles, and it didn't work, at least not for me. The final scene, which featured two scanners in a battle to the death, was the most ridiculous of all ... if one actor overdoing the facial palsy was too much, two actors was over the top.
Patrick McGoohan has shown many times over what a fine actor he is, and he comes across best here, precisely because he is not a scanner, which means he gets to use all of his acting skills rather than just his face. Michael Ironside is another actor who has proven himself over time, and he has some good moments here, but he is also a scanner, which means he is often handicapped by having to rely on his face. Meanwhile, there's Stephen Lack, a painter with little acting experience, which is clear in Scanners, and Jennifer O'Neill, best remembered for her long "Cover Girl" advertising work. No, the acting isn't great in Scanners.
Still, there is the most famous scene, and I'm going to spoil it here, so don't look if you're planning on watching Scanners any time soon.