Watching Carmack's keynote in QuakeCon2012 is really interesting in many ways:
1 - A case study of how you can maintain your energy in a 3.5 hour talk.
2 - Passion of a man.
3 - Respect for the audience.
4 - How context affects the relevance of phenomena.
5 - Lots of informative tidbits from a matured code guru.
http://www.youtube.com/watch?v=wt-iVFxgFWk