If you haven't played Lost Coast with the commentary on, you should try it. It's cool. There are these little floating word bubbles at various places on the map, and you just click them to hear about different aspects of the level. They mostly focus on HDR, some of which I don't get, but there are a few, by Robin Walker, I believe, where he talks about level design and level philosophy that I found incredibly interesting. I would seriously shell out cash money for a version of Half-Life 2 (or the original Half-Life) that had audio commentary. I just eat that stuff up. I'm considering buying that Chronicles of Riddick game just because it has audio commentary. Seriously.