I can never imagine having as much knowledge of any programming language as Casey does. After only programming for a year now, it blows my mind that anyone can know and explain programming as well he does.
If you find yourself still seriously programming after a few years, try evaluating this position then.
Still I think in my position I am qualified to say that Casey is exceptionally good at explaining programming.
(He has praised Turbo C several times - probably his favorite environment in the 90's, never matched these days in some ways... )