He left us absolutely amazed at what we could do and he was eager to intern with us the next summer.
Something about working with -- or even just talking with -- truly excellent programmers does wonders for one's humility. I can still remember a few questions I've asked right here on PerlMonks which got answers that truly humbled me.
I think one of the best experiences a novice/intermediate programmer can have is to be humbled by those much better than them. I know it's helped me have a more open mind and pay much more attention to my own design and code. I'll have to remember to ask about those kinds of experiences when next I'm asked to hire developers. ;)
A collection of thoughts and links from the minds of geeks
The Code that can be seen is not the true Code
I haven't found a problem yet that can't be solved by a well-placed trebuchet