It's from a few years ago but here is Michael Abrash's experience with working at valve http://blogs.valvesoftware.com/abrash/valve-how-i-got-here-what-its-like

It's from a few years ago but here is Michael Abrash's experience with working at valve http://blogs.valvesoftware.com/abrash/valve-how-i-got-here-what-its-like-and-what-im-doing-2/ http://blogs.valvesoftware.com/abrash/valve-how-i-got-here-w... + some interesting tibits about his past at Id and MS.