Although I don't doubt that Carmack said he specifically wants the game to run at 60fps... I saw juttering in the video. I usually have an eye for it, and can't stand watching movies at 24fps on a 60hz display.
Again: 1) judder 2) You're watching a video. A video. Not the game playing. 3) As you mention, judder comes from watching 24fps movies on a 60hz display. Watching 30fps on a 60fps display would not cause any judder. 4) You're watching a video. It's worth repeating. If I take video footage running at 9 bazillion fps and convert it to a video that's not a factor of 60 then you'll get judder on a 60hz monitor. Heck, if I run a game at 72fps then I'll likely get some judder on a 60 hz monitor.