His thesis is a fascinating read, although we warn you that much of it is academic. For those of you looking for a fun, atmospheric title, we recommend you try out flOw, a game developed by Chen as an implementation of DDA in a gaming environment. The game's ambiance is enough to recommend a play-through -- you can even download the title for offline play (available for both PC and Mac).
We have harped on difficulty and game balance before; it will always be a point of discussion among game theorists and game designers. While DDA theoretically sounds like a great idea (a game that always challenges you? Sign me up!), it becomes increasingly less pliable once you start worrying about implementation. How challenging do we make it? Will the relative difficulty undulate? What variables should one adjust in deciding how to vary the challenge? The answers to those questions, unfortunately, are less clear.
Gamer's Room 101: the argument FOR balance
Gamer's Room 101: the argument AGAINST balance
Making games "universally accessible"