I love how scientific he is when he talks and evidently when he does his work. He said something along the lines of "if you can't decide which way to do something, do it both ways and see which is better".

Refreshing to hear a talk like that amongst discussions around language, platform wars.

He always looks like that, it's great :) You should see him demoing the iPhone version of his engine: https://www.youtube.com/watch?v=keu4GiTGQ6M

i'll warrant his ability to tap into his inner passionate, geeky 16-year-old is what has made him a legend in the first place.

Yep, in a recent QuakeCon he stated that he's more passionate now and having more fun now than ever. Great guy.

It's like he's just doing a science project. That's totally amazing.