I was 8 years old when I saw it -- no movie has influenced me like that one. At that age, the star gate scene was kind of scary; but, yes, the HAL 9000 had a _huge_ impact on me. One of the best films, ever.
Having only seen in on TV (multiple times) I saw the 70mm version at a local cinema recently. Amazing experience, and it holds up remarkably well IMHO.