I saw 2001 on a big screen in Sydney in either 2001 or 2002. It was one of the best cinematic experiences of my life. (I'd already seen it on video).

There were no ads before hand, no "lets all go to the lobby to get snacks crap". You came in and sat down. The lighting was subdued. There was really faint ambient music. Eventually the lights went out. The movie started. The whole thing was dazzling on what was one of the larger screens I've seen in a cinema. I took a girl along who'd never seen it before - she was blown away, and she was a film student at the time.

2001 is one of my favourite films of all time, and one of the best films ever made, IMO. The word "genius" gets used a lot, but Kubrick and Clarke both live up to that title...