Valve first tried out designer commentary with the Lost Coast standalone demo. Apparently it was such a big success that they decided to do the same for all the games in the Orange Box.
Now Valve is a group of some very, very smart people, and it shows.
Generic behind-the-scenes specials tend to tell the same old story: the development cycle was hectic, but the team eventually persevered and released a great product (even if it was a little flawed and missing some features). In between all that you might come across an interesting tid-bit or two, but don’t expect any mind blowing revelations.
The commentary on the Orange Box, though, is full of pure-gold nuggets. In fact, playing through its four commentary-enabled titles will probably teach you more about various aspects of videogame production than any game design book. If you haven’t checked it out but are in any way interested in videogame design, I urge you to do so now.
Here are just a few segments I picked out: